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The Effects of Quality Grade, Aging and Location on Selected Muscles of Locomotion of the Beef Chuck and Round


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THE EFFECTS OF QUALITY GRADE, AGING AND LOCATION ON SELECTED MUSCLES OF LOCOMOTION OF THE BEEF CHUCK AND ROUND By CHRISTY LYNN GREENHAW BRATCHER A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL F ULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2004

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Copyright 2004 by Christy Lynn Greenhaw Bratcher

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iii ACKNOWLEDGMENTS First and foremost I want to thank God for bringing me to this point in my life. Without my trust in Him, I would have never made it here considering all that I have dealt with for the last two years. So to God be my glory. I would also like to thank my husband, Mike, for all the support he has given me not only throughout my graduate program, but also through my undergraduate program and in everything else I have attempted. Unfortunately, he missed out on being here for the most part o f my masters program, as he was in Iraq serving our great United States of America. He is a hero to all. He spent thirteen months away from home and still managed to lend support through his words the entire time he was away. I am also so proud of him for completing his bachelors degree in exercise and sports science this spring after being out of school for three and a half semesters. I also owe great gratitude to all of my friends who have brought me through this time of my life. There are a number of people who have been there for me, and I would like to thank them all: Deke Alkire, Liz Johnson, Nathan and Wimberley Krueger, Alex Stelzleni, Davin Harms, Ben Butler, Paul Davis, and also my friends and co workers in the University of Florida Meats Pro cessing Center: Byron Davis and Tommy Estevez. The Meat Processing Center manager, Larry Eubanks, and his wife, Kathleen, who have been my family away from home throughout my school career, both receive my debt of gratitude. Larry interested me in attendi ng graduate school and has lent support in numerous ways to Mike and me since we have known him. I also owe a thank you to

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iv Dr. Dwain Johnson for his guidance and support and extreme patience throughout my degree, and to the rest of my committee: Drs. Sall y K. Williams and Ronald H. Schmidt. Last but most definitely not least, I would like to extend my gratitude to my brother, Michael; my grandparents, Glenn and Lutherene Greenhaw and H.C. and the late Faye Childers; close family friends Phil and Jeanette C arter; and the rest of my family and Mikes family. But most of all, I would like to thank my parents, Walter and Glenda Greenhaw, who have lent undying love and support to me for my life and school career. They have been my strongest supporting foundati on and my biggest fans. I am forever indebted to them for all they have done for me.

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v TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ iii LIST OF TABLES ................................ ................................ ................................ ............ vii LIST OF FIGURES ................................ ................................ ................................ ......... viii ABSTRACT ................................ ................................ ................................ ....................... ix CHAPTER 1 INTRODUCTION ................................ ................................ ................................ ........ 1 2 REVIEW OF LITERATURE ................................ ................................ ....................... 3 Tenderness ................................ ................................ ................................ .................... 3 Factors Affecting the Tenderness of Beef ................................ ............................. 5 Measurement of Tenderness ................................ ................................ .................. 6 Aging ................................ ................................ ................................ .......................... 10 Mechanism of Aging ................................ ................................ ........................... 11 Length of Aging ................................ ................................ ................................ .. 13 Rate of Muscle Aging ................................ ................................ .......................... 15 Quality Grade ................................ ................................ ................................ .............. 17 Association of Level of Marbling and Quality Grade to T enderness .................. 18 The Insurance Theory ................................ ................................ ...................... 20 Differences Detected by Consumers ................................ ................................ ... 21 Location ................................ ................................ ................................ ...................... 23 3 THE EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON WBS FORCE VALUES ON SELECTED MUSCLES OF LOCOMOTION OF THE BEEF CHUCK AND ROUND ................................ ................................ ............................. 27 Introduction ................................ ................................ ................................ ................. 27 Materials and Methods ................................ ................................ ............................... 30 Results and Discussion ................................ ................................ ............................... 32 Implications ................................ ................................ ................................ ................ 36

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vi 4 EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON COOK AND THAW LOSS OF SELECTED MUSCLES OF LOCOMOTION OF THE BEEF CHUCK AND ROUND ................................ ................................ ............................. 42 Introduction ................................ ................................ ................................ ................. 42 Materials and Methods ................................ ................................ ............................... 44 Results and Discussion ................................ ................................ ............................... 46 Implications ................................ ................................ ................................ ................ 49 5 CONCLUSIONS ................................ ................................ ................................ ........ 55 LIST OF REFERENCES ................................ ................................ ................................ ... 57 BIOGRAPHICAL SKETCH ................................ ................................ ............................. 66

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vii LIST OF TABLES Table page 3 1. Means, standard deviations, minimum, and ma ximum values for WBS at 14 days postmortem aging by muscle ................................ ................................ .................... 38 3 2. WBS values for muscles of the chuck and knuckle averaged acro ss all aging periods ................................ ................................ ................................ ...................... 39 3 3. WBS values by grade and aging treatment ................................ ................................ 40 3 4. WBS values by location ................................ ................................ ............................. 41 4 1. Thaw loss for muscles of the chuck and knuckle averaged across all aging periods ................................ ................................ ................................ ...................... 50 4 2. Cook loss for muscles of the chuck and knuckle averaged across all aging periods ................................ ................................ ................................ ...................... 51

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viii LIST OF FIGURES Figure page 4 1. Thaw loss average for grades across aging periods. ................................ .................. 52 4 2. Cook loss for muscles by g rade. ................................ ................................ ................ 53 4 3. Cook loss of subprimals averaged across grade by aging period. ............................. 54

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ix Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science THE EFFECTS OF QUALITY GRADE, AGING AND LOCATION ON SELECTED MUSCLES OF LOCOMO TION OF THE BEEF CHUCK AND ROUND By Christy Lynn Greenhaw Bratcher May 2004 Chair: D. D. Johnson Major Department: of Animal Sciences The objective of this study was to determine the aging patterns of nine selected muscles from the chuck and round from two quality grades of beef: United States Department of Agriculture (USDA) Select and the upper 2/3 of USDA Choice grade. The International Meat Purchase Specifications (IMPS) (NAMP, 1988) 115 2 piece chuck was separated and the following muscles were sel ected for study: infraspinatus, triceps brachii lateral head, triceps brachii long head, serratus ventralis complexus, splenius and rhomboideus. The IMPS 167A knuckle was also separated and the vastus lateralis and rectus femoris were evaluated. Th ese muscles were selected because of the possibility of being used as cuts where tenderness is critical due to the probability that they would be cooked with a dry cooking method, based on results from the Muscle Profiling Study conducted by the University of Florida and University of Nebraska in conjunction with the National Cattlemans Beef Association. Each muscle was divided into four portions, progressing from anterior to posterior or dorsal to ventral orientation to

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x the carcass. One steak was removed from each portion for evaluation. Aging was conducted at 7, 14, 21, or 28 days. After achieving their appropriate aging treatment Warner Bratzler Shear (WBS) force analyses were conducted on an Instron (Canton, MA) universal testing machine. Aging affe cted all of the muscles evaluated in this study in a similar fashion; therefore, consistent recommendations can be given for these muscles. This study revealed that USDA grade had an effect on aging, in that it would not be necessary to hold muscles from the upper 2/3 of USDA Choice grade beyond 7 days of age. For USDA Choice grade, there was in increase in thaw loss from 14 to 28 days of aging, but aging up to 7 days had no effect. Muscles from lower marbled grades (i.e. USDA Select), should be aged a minimum of 14 days postmortem. As USDA Select grade was aged from 7 to 21 days, there was an increased percentage of thaw loss. However, after 14 to 21 days of age, it seems that there is no further increase in thaw loss percentages. The muscles respond differently depending on grade; USDA Select generally had higher cooking losses than USDA Choice. Location within a muscle had an effect on WBS values in four of the nine muscles evaluated. T his indicated that muscles would have to be treated on an indi vidual basis when fabricating and merchandising individual retail cuts from these muscles. For some muscles, location within the cut can be ignored, and for others location must be considered for tenderness enhancement or product utilization

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1 CHAPTER 1 INTRODUCTION In recent years, economic pressures have challenged the livestock and meat industries to seek ways of producing meat products that will enable consumers to receive maximum palatability benefits at the lowest costs (Morgan et al., 199 1). Due to consumer demand for smaller portion sizes, beef retailers have been forced to fabricate steaks from cuts of meat (round and chuck subprimals) that previously were merchandised solely as roasts (Shackelford et al., 1995). As the industry begins to isolate individual muscles of the chuck and round for merchandising as steak cuts, then more knowledge about how these muscles respond to postmortem aging is required in order to assure tenderness. The round represents approximately 22% of the weight of a typical beef carcass and contains some of the least tender muscles of the carcass (Ramsbottom et al., 1945; Jones et al., 2001). Savell and Smith (2000) reported that the chuck represents about 30% of the total carcass weight. Therefore, approximate ly 52% of the carcass that is currently used primarily as ground beef and roasts. The 1991 National Beef Tenderness Survey (Morgan et al., 1991) revealed problems with tenderness of beef from the chuck and round subprimals and with the top sirloin steak. The survey also found that round and chuck cuts were especially tough despite being cooked by moist heat methods. Steaks from the round and the chuck were much tougher than their roast counterparts. The mean shear force of the top round roast was 4.06 kg while the steak counterpart had an average shear force value of 5.23 kg

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2 (Savell and Shackelford, 1992). The industry must discover a way to utilize these cuts to provide for optimal utilization of the carcass while ensuring a tender cut of meat. The eco nomic incentives for the industry to improve the tenderness of beef must be established before significant improvements in the consistency and palatability of beef will occur (Miller et al., 1998). According to Miller et al. (1998), the most important fac tor in a tenderness study with consumers is to establish that a range in beef tenderness from tender to tough exists. The range given in Miller et al. (1995) is greater than 2.0 and less than 7.0 kg of shear force. Research has shown that consumers can d etect changes in tenderness similar to those found with instrumental measurements such as Warner Bratzler shear force (WBS) (Shackelford et al., 1991b; Miller et al., 1995; Boleman et al., 1997). Therefore, WBS values can be used as an indicator of the va lue relationship for tenderness. Some possible factors that affect tenderness have been identified as postmortem storage time and temperature (aging) (Smith et al., 1978; Mitchell et al., 1991; Eilers et al., 1996;), the quality grade of the carcass (Goll et al., 1965; McBee and Wiles, 1967; Smith and Carpenter, 1974), and a possible location effect within individual muscles (Kerth et al., 2002; Reuter et al., 2002; Rhee et al., 2004). Continued work is needed on improving meat tenderness, primarily for re tail cuts from the round and chuck. It is necessary to get and increased percentage of steaks from the carcass or increase the percentage of muscles that can be used for steak cuts. If consumers are willing to pay more for guaranteed tender beef products (Boleman et al., 1997; Kukowski et al., 2004), it is the industrys job to discover innovative ideas to produce guaranteed tender beef.

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3 CHAPTER 2 REVIEW OF LITERATURE Tenderness Consumers have ranked tenderness as being the most important factor influencing satisfaction (Savell et al., 1987, 1989; Smith et al., 1987). The final report of the 1995 National Beef Quality Audit listed low ove rall palatability and inadequate tenderness among the top 10 concerns of the beef industry (Smith et al., 1995). In addition, during the National Beef Tenderness Symposium (National Cattlemens Association, 1994) it was revealed that 1) one in every four steaks is less than desirable in tenderness and overall palatability (Smith et al., 1992), 2) one tough carcass may affect as many as 542 consumers (Harris and Savell, 1993), and 3) beef industry leadership is adamant about increasing market share, with in creasing beef tenderness being the key to this change in positioning (George et al., 1997). The 1998 National Beef Tenderness Survey (Brooks et al., 2000) collected samples from 56 retail stores representing 15 retail chains and 14 foodservice facilities i n eight U. S. cities. Steaks were divided into the following quality groups for statistical analysis: Prime, Top Choice, Choice, Select, and Lean or No Roll. Average postfabrication aging times were 32 days for foodservice subprimals and 19 days for reta il cut samples. The percentages of retail top round, eye of round, and bottom round steaks with a Warner Bratzler shear (WBS) force of greater than 3.9 kg, the 68% confidence level of Shackelford et al. (1991b), were 39.5, 55.9, and 68.0, respectively. T hese data indicate that improvements in the tenderness of retail cuts from the round are needed. Quality

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4 group had little or no effect on consumer sensory evaluations and WBS values of retail and foodservice steaks used in this study. Consumers can differ entiate among steaks varying in WBS (Miller et al., 1995; Huffman et al., 1996). As WBS decreased, tenderness scores increased, indicating that consumers could detect changes in tenderness similar to those found in instrumental measurement (Miller et al., 1998). Consumers are also willing to pay more for steaks that reach a certain level of tenderness (Miller et al., 2001). If there is a possibility of increasing tenderness in these cuts of beef, the value of the total carcass can be increased. Boleman et al. (1997) also suggested that consumers can discern between categories of tenderness and are willing to pay a premium for improved tenderness. In this study, strip loins were cut into 2.54 cm thick steaks, and the center steak from each strip loin was used to determine WBS. The remaining steaks were placed into one of the following categories based on that WBS and color coded accordingly: 1) 2.27 to 3.58 kg (Red); 2) 4.08 to 5.40 kg (White); and 3) 5.90 to 7.21 kg (Blue). A $1.10/ kg price difference was placed between each category and randomly recruited consumers were allowed to evaluate steaks and purchase them based on their findings. Consumers gave higher tenderness ratings to Red steaks than to Blue steaks. Overall satisfaction was higher (P<0 .05) for Red steaks than for the other two categories. The following percentages of steaks were purchased: 1) Red, 94.6%; 2) White, 3.6% and 3) Blue, 1.8%. These results suggested that consumers could discern between tenderness categories and were willin g to pay a premium for improved tenderness. Therefore, the factors that affect tenderness need to be identified and studies need to be conducted to determine the best way to ensure a tender product.

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5 Factors Affecting the Tenderness of Beef Differences in the rate and extent of postmortem tenderization are the principle sources of variation in meat tenderness and are probably the source of inconsistency in meat tenderness at the consumer level. To solve the tenderness problem, even greater understanding of the mechanisms regulating meat tenderness and tenderization must be gained (Koohmaraie et al., 1996). Tenderness is extremely difficult to measure objectively because the chewing motions involved in mastication involve both vertical and lateral movements of the human jaw as well as various in between modifications, which together produce the impression of tenderness (Pearson, 1963). Before 1960, theories about meat tenderness tended to be dominated by the role of connective tissue (Locker, 1985). Locke r (1960) demonstrated the importance of the myofibrillar component of tenderness and began the modern era of meat tenderness research. Tenderization begins either at slaughter or shortly after slaughter, which results from weakening of the myofibrils caus ed by proteolysis of proteins responsible for maintaining structural integrity of the myofibrils (Wheeler and Koohmaraie, 1994). Aging, a method for tenderization of meat by storage at above freezing temperatures in vacuum bags, is very important to assur e a tender, acceptable product (Davey et al., 1967). There are various theories about the reason for this phenomenon. Location within muscles also has been shown to play a role in tenderness variations. There are tenderness differences among muscles wit hin the beef wholesale round, and these differences are well documented (Ramsbottom et al., 1945; McKeith et al., 1985; Johnson et al., 1988; Jones et al., 2001; Reuter et al., 2002). It has been established that a tenderness gradient exists within steak s obtained for the longissimus muscle (Alsmeyer et al., 1965; Sharrah et al., 1965; Smith et al., 1969). Another factor that may affect tenderness is quality

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6 grade. Romans et al. (1965) found steaks containing moderate degrees of marbling to be juicier t han steaks possessing slight marbling although marbling level did not have a significant effect on tenderness as determined by WBS. Walter et al. (1963) reported that marbling did not exert any significant effect on tenderness, flavor or juiciness scores. Research reviews (Jeremiah et al., 1970; Parrish, 1974; Smith and Carpenter, 1974) have emphasized low relationships between marbling and tenderness. Numerous investigation of the relationship between marbling and beef palatability have shown that, alth ough there is a positive relationship between marbling degree and tenderness, this relationship is weak at best (Parrish, 1974). Wheeler et al. (1994) reported that marbling explained about 5% of the variation in palatability traits and that there was bot h tough and tender meat within each marbling degree. So it is important to take into account these factors when trying to determine the ideal way to create a predictability acceptable product to the consumer. Measurement of Tenderness Because of savings i n time and money and the difficulty of maintaining a well trained sensory panel, tenderness of cooked meat samples can be assessed much more easily via WBS than trained sensory panel analysis (Shackelford et al., 1995). Harris and Shorthose (1988) state t hat shear force does not accurately reflect tenderness differences among muscles, however most investigators rely upon the WBS machine for objective estimates of tenderness (Smith et al., 1978). Results of correlations between sensory panel tenderness rat ings and WBS values for the same muscles have suggested that WBS is sufficiently reliable to use in lieu of taste panel results (Brady, 1937; Hay et al., 1953; Kropf and Graf, 1959; Doty and Pierce, 1961; Pearson, 1963; Alsmeyer et al., 1966).

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7 Shackelfor d et al. (1995) determined the relationship between WBS and overall tenderness of 10 major beef muscles. Mean WBS differed little among muscles; however muscles differed (P<0.05) greatly in overall tenderness ratings (psoas major (PM) = infraspinatus (IF) > triceps brachii (TB) = longissimus dorsi (LD) = gluteus medius (GM) = supraspinatus (SS) > biceps femoris (BF) = semimembranosus (SM) = quadriceps femoris (QF)). These differences in overall tenderness among muscles were consistent with previous finding s of Ramsbottom and Stradine (1948), Shorthose and Harris (1990), and Morgan et al. (1991). WBS was effective in detecting that PM and IF were more tender than the others, but failed to detect and differentiate between the other muscles studied. Differen ces in overall tenderness ratings among TB, LD, ST, GM, SS, BF, SM, and QF could not be explained with any of the parameters of the WBS profile. The relationship between peak load and overall tenderness within each muscle ranged from very weak for GM (r 2 =0 .00 to strong for LD r 2 =0.73) (Shackelford et al., 1995). Some researchers have proposed relationships between WBS and consumer perceptions of degree of tenderness. Shackelford et al. (1997a) classified a carcass as tender, intermediate or tough i f its longissimus shear value at one or two days postmortem was < 6 kg, 6 to 9 kg, or > 9 kg, respectively. A total of 100% of the carcasses in the tender class had low WBS values at 14 days postmortem, 81% (exp 1) and 85% (exp 2) of the carcasses in the intermediate class had low WBS values at 14 days postmortem, and 74% (exp 1) and 67% (exp 2) of the carcasses in the tough class did not have low WBS values at 14 days postmortem. In correlation studies, WBS values were highly correlated with sensory tenderness (r = 0.78), which agrees with the work of Webb et al. (1964). Sensory tenderness, juiciness, and flavor were also

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8 highly correlated with each other. Shackelford et al. (1991b) reported that 82% of samples having WBS values less than 4. 6 kg were rated slightly tender or higher, and 66% of samples having WBS values greater than 4.6 kg were rated less than slightly tender by an in home consumer panel. However, the relationship between tenderness of the longissimus and tenderness of ot her muscles had been reported to be weak to moderate (Slanger et al., 1985; Shackelford et al., 1995). Thus a minor muscle probably could not be used as an indicator of longissimus tenderness. There would be limited benefit to classifying the tenderness of other cuts based on tenderness of the longissimus muscle (Shackelford et al., 1999). There would likely not be much opportunity to classify round cuts according to tenderness, on any basis, because Shackelford et al. (1997b) demonstrated that there is l ittle animal to animal variation in the tenderness of round cuts from youthful grain fed steers. Morgan et al. (1991) showed that WBS values indicate that a high percentage of retail cuts from the chuck and round would receive overall tenderness rating sc ores less than slightly tender. Tenderloin and top blade steaks, which are consistently very tender (Shackelford et al., 1995) could be guaranteed tender without product testing. However, round cuts, which have a lot of random variation within each car cass (Shackelford et al., 1997b), should not be guaranteed tender regardless of longissimus tenderness (Shackelford et al., 1997a). Beef palatability research studies often use traits such as marbling score, WBS, and consumer or trained taste panel evaluat ions of tenderness, juiciness and flavor as indicators of beef palatability (Platter et al., 2003). Platter et al. (2003) revealed moderate to high correlations (P < 0.05) among mean marbling scores, WBS, and mean

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9 consumer panel palatability ratings. The correlation between consumer tenderness ratings and WBS was moderately high (r = 0.63). Marbling scores were correlations with WBS, consumer tenderness ratings, consumer juiciness ratings, and consumer flavor ratings were r = 0.31, 0.27, 0.34, 0.22, respectively. High, positive correlations (r = 0.80 to 0.84) were observed among all consumer sensory ratings (Platter et al., 2003). Of the three sensory models developed by Platter et al. (2003), the most accurate was the consumer tenderness rating at r 2 =0.56. The marbling and the WBS models were r 2 =0.053 and 0.225 respectively, for determining whether two thirds of consumers would have rated steaks as acceptable. Slice force is another measurement of tenderness that has been studied. Wheeler et al (1999) established the longissimus dorsi to be tender if the day three WBS was < 5.0 kg when cooked to 70C. This value was equivalent to 23 kg of slice shear force that Shackelford et al. (1999) used to test the efficacy of tenderness classification. T rained sensory panel is also a measurement of tenderness in many studies. Smith et al. (1978) demonstrated that the correlation for overall tenderness rating for 14 muscles and shear force values was r = 0.48. These data suggested that shear force and se nsory panel tenderness ratings are sufficiently correlated to justify use of either measure for assessing the tenderness of muscles in a beef carcass (Smith et al., 1978). However, Lorenzen et al. (2003) reported a low correlation between trained sensory panels and consumer sensory panels. There is an inherent difficulty in predicting consumer responses from objective laboratory procedures, such as trained sensory panels and WBS. There will continue to be important future uses for trained sensory panels, WBS determination, and in home or other consumer evaluations of meat. How they can be

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10 used to predict each other is a question that will be asked by meat science researchers for years to come (Lorenzen et al., 2003). Aging Aging, a method for tenderizi ng of meat by storage at above freezing temperatures in vacuum bags, is very important to assure a tender, acceptable product (Davey et al., 1967). Retailers and purveyors have relied on aging as a means of controlling beef quality (Savell and Shackelford 1992). Although aging is important in assuring tender acceptable retail products, it creates problems in merchandising and in use of storage facilities due to increased inventory of beef (Davey et al., 1967). This problem could be alleviated by identif ication of the minimum period of aging necessary to assure the desired level of tenderness (Smith et al., 1978). There are two different methods of aging; wet and dry. Wet aging occurs in a vacuum bag under refrigeration. In dry aging, the product is u npackaged and exposed to air at a controlled temperature and relative humidity. Wet aging will produce acceptably tender and flavorful products without loss of yield and the necessary amount of aging space as with dry aging. For some processors, acceptab le product palatability and economic savings can be accomplished by using wet aging (Parrish et al., 1991). Parrish et al. (1991) made a comparison between wet aging and dry aging and determined that little or no cooler shrink was observed with wet aged p roduct. No measurable purge was recorded for the wet aged product either. Steaks for wet aging had higher scores (P < 0.01) for tenderness and overall palatability, although steaks from both wet and dry aging provided very palatable products. Postmorte m storage of carcasses at refrigerated temperature has been known to improve meat tenderness for many years and still remains an important procedure for

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11 producing tender meat. Although improvement in meat tenderness is measurable both subjectively and obj ectively, the exact mechanism of improvement in tenderness as a result of postmortem storage still remains unclear. However there appears to be general agreement that proteolysis of myofibrillar protein is the major contributor to meat tenderization durin g postmortem storage (Dutson, 1983; Goll et al., 1983). Mechanism of Aging Tenderization begins either at slaughter or shortly after slaughter, which results from weakening of the myofibrils caused by proteolysis of proteins responsible for maintaining s tructural integrity of the myofibrils (Wheeler and Koohmaraie, 1994) There are some animals that go through the tenderization process rapidly and could be consumed after 1 day, whereas others could be consumed after 3, 7, or 14 days, and still others wou ld not be acceptable even after extended post mortem storage (Wheeler and Koohmaraie, 1994). The mechanism of postmortem aging is a very controversial issue and many researchers have made an attempt to determine the specific mode of action. Smith et al. (1978) demonstrated a characteristic improvement in beef tenderness during postmortem aging in response to myofibrillar protein degradation by endogenous proteases. Koohmaraie (1995) suggested that calpain mediated proteolysis of key myofibrillar proteins is responsible for improvement in meat tenderness during post mortem storage of carcasses or cuts of meat at refrigerated temperatures. Differences in the potential proteolytic activity of the calpain system result in differences in the rate and extent of post mortem tenderization. Koohmaraie (1995) has collected evidence indicating that, within a species, 24 hr rather than at death, calpastain activity is related to meat tenderness. In beef, for example, calpastatin activity at 24 hr post mortem is high ly

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12 related to beef tenderness after 14 days of postmortem storage. The estimates for the relationship between calpastatin activity and meat tenderness vary, but up to 40% of the variation in beef tenderness is explained by calpastatin activity at 1 day po st mortem (Koohmaraie, 1995). Although endogenous enzyme systems are capable of softening or degrading collagen (Dutson et al., 1980; Kopp and Valin, 1980 81; Wu et al., 1981), those enzymes have not been shown to be released in sufficient quantities post mortem to initiate such changes (Harris et al., 1992). Calcium activated factor (CAF), also known as calcium dependent protease (CDP), is an endogenous structural protease active in postmortem beef muscle and is responsible for myofibrillar protein degrad ation (disappearance of Troponin T and appearance of a 30,000 Dalton component) indicating postmortem aging (Olson et al., 1977). Of the proteases located inside skeletal muscle, CDP and lysosomal enzymes appear to be the best candidates for bringing abou t the tenderness changes during postmortem storage (Dutson, 1983; Goll et al., 1983). CDP was initially identified in skeletal muscle by Busch et al. (1972) and later purified by Dayton et al. (1976). Mellgren (1980) reported the existence of a second fo rm CDP. These two forms of the protease are now referred to as CDP I and CDP II, according to the sequence of elution from a DEAE cellulose column at pH 7.5. CDP I requires only very low concentration of calcium for 50% activation, whereas CDP II require s much higher calcium concentration (Goll et al., 1983). CDP I has also been labeled calpain, and CDP II as m calpain. Both of these proteases are located primarily in the cytosol. A second group of proteases that have been implicated in postmortem t enderization are lysosomal enzymes. Of 13 reported lysosomal enzymes, only 7 have been shown to

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13 exist in the lysosome of skeletal muscle cells (Goll et al., 1983). These enzymes have acidic pH optima and, therefore, if involved in postmortem tenderizatio n, they are most involved once muscle approaches its ultimate pH. To explain a basis for meat tenderization during postmortem storage, it has been postulated that one class of these proteases or the synergistic action of both classes of proteases (CDPs a nd lysosomal enzymes) is responsible for postmortem changes (Dutson, 1983; Goll et al., 1983; Pearson et al., 1983). It is logical to assume that the class of proteases responsible for postmortem aging should have higher activity in the carcasses with a h igh aging response and vice versa (Koohmaraie et al., 1988). Illian et al. (2001) reported a third CDP, and stated that the primary role of CDP I and CDP III was associated with meat tenderness in vivo due to the high activity of these two enzymes. Lengt h of Aging Another question that arises with the phenomenon of postmortem aging is how long meat should be aged to reach optimum tenderness. Smith et al. (1978) stated that aging of US Choice beef carcasses for 11 days will optimize tenderness, flavor, an d overall palatability of the majority of muscles in steaks and (or) roasts from the chuck, rib, loin, and round when such cuts are ultimately broiled or roasted. Compared to shear force at 5 days, aging for 8 days, 11 days, 21 days, and 28 days decreased shear force. This was the case for sensory panel ratings also; aging for 11 days appeared to produce optimal tenderization since further aging did not accomplish further reductions in shear force (Smith et al., 1978). Doty and Pierce (1961) reported that aging of raw wholesale cuts for two weeks substantially reduced shear force, but further aging did not result in further shear force reductions.

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14 Brooks et al. (2000) found that subprimal postfabrication times at the retail level averaged 19 days. Overall foodservice steaks were subjected to a postfabrication time of 32 days. Interestingly, top sirloins were aged an average of 32 days with a minimum of 20 days before fabrication in an effort to maximize tenderness. However, Harris et al. (1992) reported that aging top sirloins up to 35 days postmortem had no effect on WBS values. Lorenzen et al. (1998) reported that postmortem aging times of 14 days maximized the tenderness of steaks from the chuck roll, rib, and shortloin. Reducing the number of cuts t hat are not sufficiently aged before consumption may help increase tenderness ratings and further reduce beef tenderness problems (Brooks et al., 2000). Harris et al. (1992) found that top sirloin steaks did not respond to aging until 28 days while top lo in steaks demonstrated improvement in muscle fiber tenderness after only 7 days of postmortem aging and another increase after 28 days. Top sirloin steaks had higher (P < 0.05) shear force values than did top loin steaks at each aging period. The top sir loin steak demonstrated no decrease in WBS values in response to postmortem aging (Harris et al., 1992). Connective tissue concentration also plays a major role in the aging process. Connective tissue tended to remain relatively stable and intact during aging. If the top sirloin steaks were less tender due to higher concentrations of connective tissue, this lack of WBS decline would be expected (Harris et al., 1992). Overall in the study, the top loin steaks showed a relatively steady decrease in shear force values as postmortem aging time increased. Miller et al. (1997) found that aging beef for 14 days improved the consistency of beef tenderness and should be recommended as a processing control point for the beef industry. This method would improve consumer acceptance of beef regardless of breed,

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15 fatness, or processing variables. When steaks were aged for 7 days, WBS values of Choice steaks tended to be more tender initially (6.6 kg) than Select steaks (6.1 kg). However, aging for 14 days removed t he grade effect (6.8 kg for Choice and 6.7 kg for Select). The additional 7 days of aging raised the WBS of Choice steaks 0.26 kg but raised the WBS of Select steaks twice as much (0.52 kg). Sustained tenderness scores showed a similar pattern. If aged for 7 days, Choice steaks (6.5 kg) were scored higher than Select steaks (6.0 kg). However, aging for 14 days removed the grade effect (6.7 kg vs. 6.5 kg). Choice steaks aged for 7 days were scored the same as Select steaks aged for 14 days (6.5 kg) (Mil ler et al., 1997). Rate of Muscle Aging Tenderization of different muscles during aging in an individual carcass has been shown to vary (Koohmaraie et al., 1988; Ouali and Talmant, 1990). For example, the rate of tenderization of longissimus thoracis et l umborum (LT) was different for that of the psoas major (PM) (Cridge et al., 1994). Rate of tenderization over the 14 day aging period of LT was significantly (P < 0.05) higher than that of PM. These observations are in accord with the results obtained by Koohmaraie et al. (1988) for the same two muscles in the bovine (Ilian et al., 2001). Therefore, the rate of tenderization within various muscles of the carcass needs to be considered when making recommendations about aging. Koohmaraie et al. (1988) dem onstrated that at 24 hour postmortem longissimus (L), biceps femoris (BF), and psoas major (PM) muscles differed significantly in their shear force values, but after 14 days of aging these differences were reduced considerably. In terms of the aging respo nse, L had the greatest response with a lesser response in BF, and no response at all in PM at day 14. In this study the activities of catheptic enzymes, B, H, L as well as the activities of CDP I and II were examined in an

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16 attempt to identify which prote ase class might be responsible for the observed differences seen in aging response. Results indicated that regardless of the differences seen in aging response, activities for cathespins (B, H, and B+L) were the same for all three muscles. However, it ma y be possible that these enzymes could be differentially activated in vivo by higher temperature and/or lower pH (Dutson, 1983) as seen in the PM muscle, thus causing more aging response at the same enzyme concentration. In the case of CDP, activities fol lowed the same pattern as the aging responses; L which had the highest aging response also had the higher CDP I activity. In turn, PM, which displayed the least aging response had the lowest CDP I activity, and BF was intermediate in both CDP I activity a nd aging response. Based on the results of this and other experiments (Koohmaraie et al., 1986, 1987) it was concluded that the initial levels of CDP I activity determine the aging response of a given muscle. The reason PM muscle had no aging response, e ven though its CDP activity was about 50% of the L muscle, is not known. Koohmaraie (1987) has demonstrated that about 50% of the aging response is completed by 24 hr postmortem. Sarcomere length may also be related to the aging response in that the musc les with shorter sarcomere lengths had a greater aging response. At present no mechanism for a relationship between sarcomere length and aging response can be proposed, however, Dutson et al. (1976) demonstrated greater ultra structural alterations of z l ines when both psoas major and sternomandibularis muscles were shortened. If CDP I activity is responsible for postmortem changes in the muscle, then its inactivation or unfavorable conditions for its activation should prevent postmortem changes in the mu scle. Also activation of CDP I or generation of favorable conditions for its activation should

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17 accelerate the postmortem changes. This particular point in now being addressed by attempting to manipulate animals and/or carcasses so that CDP I would not be activated and then examining postmortem changes in these carcasses (Koohmaraie et al., 1988). Quality Grade Marbling has often been implicated as a contributing factor to beef palatability and is a major component in the USDA beef grading system (Jennings et al., 1978). Romans et al. (1965) found steaks containing moderate degrees of marbling to be juicier than steaks possessing slight marbling although marbling level did not have a significant effect on tenderness as determined by the WBS. Also, Walter et al. (1963) reported that marbling did not exert any significant effect on tenderness, flavor or juiciness scores. Research reviews (Jeremiah et al., 1970; Parrish, 1974; Smith and Carpenter, 1974) have emphasized low relationships between marbling and tenderness. Numerous investigations of the relationship between marbling and beef palatability have shown that, although there is a positive relationship between marbling degree and tenderness, this relationship is weak at best (Parrish, 1974). Wheeler e t al. (1994) reported that marbling explained about 5% of the variation in palatability traits and that there was both tough and tender meat within each marbling degree. Data by Wheeler et al. (1994) indicated a small, positive relationship of tenderness and juiciness with marbling score, and a variation in tenderness may be decreased slightly as marbling increases. The data also revealed a large amount of variation in sensory tenderness rating and shear force within one marbling score or another. Various studies (Blumer, 1963; Pearson, 1966; Parrish, 1974; Jeremiah, 1978) have revealed that between 5 and 10% of the variation in tenderness can be accounted for by marbling degree. According to Smith et al. (1984), due to the USDA quality grading

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18 standards for carcass beef and their implied segregation of meat based on palatability, the US beef industry has placed a high value on marbling at the 12 th rib interface of the longissimus thoracis. The emphasis on marbling in determining carcass value is based on the slight increases in juiciness, flavor, and tenderness that are obtained as marbling is increased. There are, however, several problems with palatability estimation based solely on marbling score. An abundance of research expanding over the last 30 y ears has indicated that marbling/intramuscular fat has a low relationship to palatability. The variation in marbling in the longissimus thoracis has little effect on palatability of other muscles (Smith et al., 1984). The pursuit of higher amounts of mar bling, however, results in more time on feed and, thus, in fatter, lower yielding carcasses. Use of a visual assessment of the amount of fat exposed in a cross section of the longissimus thoracis at the 12 th rib as the primary determinant of the value of the entire carcass may not be justified (Wheeler et al., 1994). Association of Level of Marbling and Quality Grade to Tenderness Many researchers have reported that tenderness, juiciness, and flavor increase with increasing degrees of marbling in a direct, linear relationship (McBee and Wiles, 1967; Jennings et al., 1978; Dolezal et al., 1982), whereas others have reported very low or nonexistent associations (Carpenter et al., 1972; Parrish et al., 1973; Parrish 1974, Dikeman and Crouse, 1975; Davis et al. 1979; Smith et al., 1984; Brooks et al., 2000). Mean WBS differences seem to be small between chuck cuts from different quality grades. However, the frequency distribution of shear force values indicates approximately 10% more cuts from Select (24 of 5 8) and No roll (36 of 87) grades having 4.0 kg of force or greater, compared with Choice chuck cuts (70 of 220) (Morgan et al., 1991). No noticeable differences in WBS or variation in tenderness were observed

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19 between round cuts differing in quality grade (Morgan et al., 1991). Smith et al. (1984) stated that marbling is of very limited value in explaining differences in sensory panel ratings of round steaks compared to loin and rib steaks. Morgan et al. (1991) determined that USDA quality grade failed to control the variation in panel ratings or WBS values to the degree necessary to ensure consistent beef products to the consumer. Regardless of the amount of external fat, loin steaks possessing modest or above marbling, had lower WBS values and higher ten derness and juiciness ratings (P<0.05) than steaks containing slight or lower marbling (Jennings et al., 1978). Wheeler et al., (1994) reported that although mean palatability scores were in the acceptable range, regression of WBS and sensory traits on ma rbling indicates the low association of marbling score to meat palatability, despite the fact that palatability traits generally increase as marbling level increases. Carcass characteristics and measurements are low in their relationships to tenderness at tributes with marbling scores having the highest correlations. Based on these results obtained from Jennings et al. (1978) it would appear that the influence of marbling on palatability varies depending on degree of marbling. George et al. (1997) reported that Choice rib steaks have lower (P < 0.01) WBS values at day 14 and day 28 than rib steaks from Select carcasses. Similarly, rib steaks for Choice carcasses had higher ratings (P < 0.01) for muscle fiber tenderness and overall tenderness. Quality grad es in the present study were useful for segregating carcasses according to their likelihood of yielding steaks differing in palatability and should continue to be useful until a system is identified to augment or assist the current use of differences in ma turity and marbling for such purpose (George et al., 1997).

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20 The Insurance Theory The insurance theory or the ability of marbling to maintain tender meat when cooked to high end point temperatures has been supported by some studies (Luchak et al., 1990) but not others (Parrish et al., 1973). Smith and Carpenter (1974) suggested that the insurance theory means that, by having higher degrees of marbling, the use of high temperature, dry heat methods of cookery and/or the attainment of advanced degrees of final doneness will not adversely affect the ultimate palatability of the cooked meat. Marbling would provide some insurance that the meat cooked too rapidly, too extensively, or by the wrong method of cookery would still be palatable. Fatty tissue do es not conduct heat as rapidly as lean tissue, so it is possible that marbled meat can endure higher external cooking temperatures without becoming overcooked internally. This theory suggests that dry heat cookery is suitable only for naturally tender cut s of beef such as the rib and loin from Prime, Choice, and Select carcasses and the top round, rump, and blade chuck from Prime and Choice carcasses (Smith and Carpenter, 1974). Luchak et al. (1990) reported that Select top loin steaks were tougher at high er temperatures than Choice top loin steaks. Choice steaks were also juicier, higher in fat, cooked slower, and were more tender when compared with Select steaks (Luchak et al., 1990). Parrish et al. (1991) found that Prime and Choice steaks scored more tender (P < 0.01) than Select steaks when cooked to an internal temperature of 63C. These results agreed with those reported by Smith et al. (1984), but disagreed with Goll et al. (1965) and Parrish et al. (1973) who found no statistically significant ef fect of quality grade on palatability of steaks when cooked to an internal temperature of 54C. Parrish et al. (1973) reported that internal cooking temperature of rib steaks is a much more important factor in palatability than marbling, and that degree of marbling,

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21 and its interaction with internal cooking temperature, had essentially no effect on palatability characteristics. Parrish et al. (1991) found that although certain palatability attributes were statistically different between quality grades an d cuts, all were considered palatable. WBS values were significantly influenced by USDA quality grade. Steaks that graded Choice had lower WBS values than Prime or Select steaks. Choice loin steaks also received higher sensory scores for tenderness, jui ciness, and overall palatability than Select loin steaks. Prime grade loin steaks and roasts scored higher on the trained and untrained sensory panels by being more tender, juicy, and having a more intense desirable flavor. This disagreed with published data in which consumer panelists found no difference in sensory characteristics between quality grades (Francis et al., 1977; Nauman et al., 1961). Differences Detected by Consumers Neely et al. (1998) evaluated three kinds of beef steaks from four USDA q uality grade levels in four major cities on consumer satisfaction of moderate to heavy beef users. Top Choice steaks were rated higher (P < 0.05) in overall like than the remainder of the grades (Low Choice, High Select, and Low Select). Ratings for High Select top loin steaks did not differ (P > 0.05) for those for Low Choice or Low Select steaks; however, overall like ratings for Low Choice differed for ratings for Low Select. Grade had no effect (P > 0.05) on overall like among the top sirloin steaks. Top Choice top round steaks were rated higher (P < 0.05) than the other grades of top round steaks for overall like. Across all USDA quality grades, ratings for Overall like for top loin steaks were higher (P < 0.05) than those for top sirloin steaks, a nd ratings for top sirloin steaks were higher (P < 0.05) than those for top round steaks. For overall like ratings, effect of

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22 USDA quality grade was cut specific. The cut most affected was the top loin steaks which agree with the findings of Smith et al. (1987). The USDA quality grade has been a controversial topic for many decades. Some believe strongly that grades perform well in sorting and categorizing beef for the marketplace. Others believe that the relationship between marbling and palatability is too low to serve as any real basis for identification of products for consumers. Findings from Neely et al. (1998) and Smith et al. (1987) suggested that USDA quality grade may be limited in the sorting of products for the marketplace derived from the longissimus muscles, and that it has less effect on the remaining major muscle of the beef carcass. Walter et al. (1965), utilized 72 carcasses that represented maturity groups A, B and E and marbling groups moderately abundant, slightly abundant, modest small, traces, and practically devoid, as determined by USDA Official Standards for Grades of Beef Carcasses. Analysis of variance and correlation coefficients demonstrated that marbling had no effect on tenderness but that tenderness decreased with adv ancing carcass maturity. Nearly 85% of the variation in ether extract could be accounted for by marbling (r = 0.92), indicating that the subjective scoring of marbling was in close agreement with objective determinations (Walter et al., 1965). As demonst rated in numerous studies, marbling did not significantly affect tenderness (Alsmeyer et al., 1959; Blumer, 1963; Cover and Hostetler, 1960; Cover et al., 1956, 1958; Palmer et al., 1958; Tuma et al., 1962, 1963; Wellington and Stouffer, 1959). Using the same data, a nalysis of variance had no effect on sensory scores for tenderness, juiciness, or flavor (Goll et al., 1965).

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23 Location There are tenderness differences among muscles within the beef wholesale round, and these differences are well documented (Ra msbottom et al., 1945; McKeith et al., 1985; Johnson et al., 1988; Jones et al., 2001; Reuter et al., 2002). Ginger and Weir, (1958) and Christians et al. (1961) have also conducted research to show that there is indeed definable intramuscular tenderness variation within certain beef round muscles. It has also been established that a tenderness gradient exists within steaks obtained from the longissimus muscle (Alsmeyer et al., 1965; Sharrah et al., 1965; Smith et al., 1969). The cores from the medial and dorsal portion of the longissimus dorsi muscle were more tender than those from the more lateral positions. Henrickson and Mjoseth (1964) found that longissimus dorsi steaks from the ninth thoracic vertebra were significantly (P < 0.01) more tender than those from the 11 th thoracic vertebra when measured with WBS. Neither maturity, marbling or core location had a significant effect on tenderness as determined by WBS by these researchers. Such variations demonstrate that meat is not a homogenous material (Walter et al., 1965). However, researchers are not in complete agreement about this gradient. Cover et al. (1962) found that there were not any differences in cores from the longissimus dorsi. Romans et al., (1965) also found no significant core locati on differences in WBS tenderness. When evaluated by the taste panel, steaks adjacent to the ninth thoracic vertebra were slightly more tender than those adjacent to the 11 th thoracic vertebra, but these differences in taste panel tenderness were nonsignif icant, however Henrickson and Mjoseth (1964) found that the longissimus dorsi steaks from the ninth thoracic vertebra were significantly (P<0.01) more tender than those from the 11 th thoracic vertebra when measured with WBS.

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24 Shackelford et al., (1997b) te sted the effects of location and aging. Biceps femoris (BF) and semitendinosus (ST) were obtained from A maturity, grain fed, crossbred steers (n=25) at 16 d postmortem. Steaks were removed from each muscle for determination of shear force and tenderness rating at each of three locations (A=proximal end, B=center, C=distal end). They were removed from the right round of each carcass and trimmed of all subcutaneous and intermuscular fat, vacuum packaged, and held at 2C. Cuts were aged to 16 d postmortem because the National Beef Tenderness Survey (Morgan et al., 1991) indicated that the average aging time for beef round cut at US retail stores was 16 days. In agreement with Shackelford et al. (1995) comparison of multiple beef muscles revealed that tend erness rating was higher for BF than for ST (P < 0.01). Sensory tenderness ratings were more repeatable than shear force for BF (R = 0.5 vs. 0.3) and ST (R = 0.6 vs. 0.56). However, all of the estimates of repeatability were much less than values that Wh eeler et al. (1997) obtained for beef longissimus using similar laboratory procedures (R= 0.79 vs. 0.9). Location did not affect (P > 0.05) BF WBS; however BF tenderness ratings were higher (P < 0.05) for location A than for locations B and C. WBS decrea sed (P < 0.05) from the proximal end to the distal end of the ST. Also, ST tenderness ratings were lower for location A than locations B and C. The proximal end of the ST contained heavy bands of connective tissue, which might explain the reduced tendern ess rating of that location. However, the increased WBS of the proximal end of ST cannot be assigned to the presence of heavy bands of connective tissue because those bands of connective tissue were avoided when removing cores for shear force. Because of the large effect of location on ST tenderness, there might be merit to target different portions of the ST for specific uses. For example, the more tender portion (distal half) of

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25 the ST might be suitable for use as broiled/grilled steaks, whereas the to ugher portion of the ST might be more suitable for use as roasts or cubed steaks (Shackelford et al., 1997b). In a similar study by McBee and Wiles (1967), steaks cut at the third lumbar vertebra were tested for differences in WBS values among dorsal, medi al and lateral locations within steaks from the longissimus dorsi. The dorsal portion had a significantly lower mean WBS value than the other two locations. There was no significant difference in WBS values between the medial and lateral locations, altho ugh the medial location had the highest mean WBS value. These results agree with those of Alsmeyer et al. (1965) and Tuma et al. (1962). A number of researchers have investigated potential tenderness gradients across the longissimus dorsi muscle (Hostetle r and Ritchey, 1964; Alsmeyer et al., 1965; Crouse et al., 1989). Kerth et al. (2002) found that core location had a significant effect (P < 0.01) on WBS in both 7 and 14 days of postmortem aging. In both aging periods there were regions of WBS values tha t differed (P < 0.05) across the cross section of the longissimus dorsi producing a tenderness gradient. In general there was a lateral to medial WBS gradient across the longissimus dorsi steaks (P < 0.05). While a dorsal to ventral gradient was evident i n both aging periods, the lateral to medial gradient was the most predominant. Cores from the center of steaks tended to have the most predictive capacity of average WBS (Kerth et al., 2002). Location effects add difficulty in merchandising steaks from ne w cuts taken from the chuck and the round. The retail sector must be innovative in merchandizing techniques to maintain steak thickness and minimize portion size (Savell and

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26 Shackelford, 1992) while taking into account the possible variations in tendernes s due to location effects. The objective of this study was to determine the aging patterns of nine selected muscles from the chuck and the round for two quality grades of beef: USDA Select and the upper 2/3 of USDA Choice. The effects of quality grade, ag ing, and location on tenderness were determined. Tenderness was determined by Warner Bratzler shear force from these nine muscles of locomotion from the two different quality grades. The muscles were also divided into quadrants to test location effects.

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27 CHAPTER 3 THE EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON WBS FORCE VALUES ON SELECTED MUSCLES OF LOCOMOTION OF THE BEEF CHUCK AND ROUND Introduction Recently, University of Florida and University of Nebraska Scientists characterized thirty seven musc les of the beef chuck and round relative to size, shape, palatability, and composition (National Cattlemens Beef Association (NCBA), 2000). This study revealed that a significant number of these muscles, when removed separately and cut across the grain, were very acceptable in sensory panel scores. The researchers concluded that there are numerous muscles that could be up graded in value by cutting them into steaks rather than selling them as part of a roast or grinding into ground beef (NCBA, 2000). Ku kowski et al. (2004) found the complexus, serratus ventralis, triceps brachii, and the infraspinatus were acceptable to consumers as steaks. By using these muscles as steaks instead of roasts, more total dollars could be generated for beef and could lead to greater profits (Kukowski et al, 2004). As the industry begins to isolate individual muscles of the chuck and round for merchandising as steak cuts, more knowledge about how these muscles respond to postmortem aging is required in order to assure tende rness. In recent years, economic pressures have challenged the livestock and meat industries to seek ways of producing meat products that will enable consumers to receive maximum palatability benefits at the lowest costs (Morgan et. al., 1991). The increa sed demand for middle cuts, combined with the decreased demand for end meats, has resulted

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28 in the average retail beef process remaining relatively unchanged during the 1990s (Kukowski et al., 2004). Due to consumer demand for smaller portion sizes, beef r etailers have been forced to fabricate steaks from cuts of meat (round and chuck subprimals) that previously were merchandised solely as roasts (Shackelford et al., 1995). With traditional roasts cuts being marketed as individual muscle steaks instead of roasts, valued could be added to the beef carcass (Kukowski et al., 2004). The round represents approximately 22% of the weight of a typical beef carcass and contains some of the least tender muscles of the carcass (Ramsbottom et al., 1945; Jones et al., 2001). Rhee et al. (2004) found that the adductor, semimembranosus, gluteus medius, and semitendinosus all from the round; and the supraspinatus from the chuck had high WBS force values (WBS = 4.29 kg). Savell and Smith (2000) reported that the chuck represents about 30% of the total carcass weight. That is approximately 52% of the carcass that is currently used primarily as ground beef and roasts. Miller et al. (2001) found that consumers w ere willing to pay a premium for steaks that reach certain levels of tenderness. One of the most prevalent and non invasive methods of postmortem tenderization is aging meat at refrigerated temperatures (Parrish, 1997). Much of the published work to da te has focused on the longissimus muscle (Jennings et al. 1978, Shackelford et al. 1991a, and Parrish, 1997). As the industry begins to isolate individual muscles of the chuck and round for merchandising as steak cuts that will be cooked commonly with a d ry cooking method, then more knowledge about how these muscles respond to postmortem aging is required. Parrish (1997) stated that tenderloin and eye of round have a different aging pattern from the longissimus muscle, but other beef muscles were not ment ioned in that review. Parrish et

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29 al. (1991) also found that beef longissimus from USDA Choice aged similarly to USDA Select longissimus, but other muscles were not studied. The economic incentives for the industry to improve the tenderness of beef must be established before significant improvements in the consistency and palatability of beef will occur (Miller et al., 1998). Kukowski et al. (2004) asked panelist to assign a price/0.45 kg (0=would not buy, 10=$10/0.45 kg). Consumers were willing to pay $5 .68/0.45 kg for the infraspinatus, and $5.15/0.45 kg for the triceps brachii. This could provide a good incentive for retailers to use these individual muscles as steak cuts. Other cuts from the Kukowski et al. (2004) study that were found to be acceptab le as steaks cuts were the serratus ventralis ($4.78/0.45 kg), and the complexus ($4.75/0.45 kg). According to Miller et al. (1998), the most important factor in a tenderness study with consumers was to establish that a range in beef tenderness from tende r to tough exists. The range given in this study was greater than 2.0 and less than 7.0 kg of shear force. Research has shown that consumers can detect changes in tenderness similar to those found with instrumental measurements such as WBS force (Miller et al., 1995; Shackelford et al., 1991b; Boleman et al., 1997). Therefore, WBS values can be used as an indicator of the value relationship for tenderness. Some possible factors that affect tenderness have been identified as postmortem storage time and te mperature (aging) (Smith et al., 1978; Eilers et al., 1996; Mitchell et al., 1991), the quality grade of the carcass (Goll et al, 1965; McBee and Wiles, 1967, Smith and Carpenter, 1974), and a possible location effect within individual muscles (Kerth et al ., 2002; Reuter et al., 2002; Rhee et al., 2004). Continued work is needed on improving meat tenderness, primarily for retail cuts from the round and chuck. If

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30 consumers are willing to pay more for guaranteed tender beef products (Boleman et al., 1997), additional work needs to be conducted to investigate aging patterns of other muscles of the chuck and round so that the highest and best use for each muscle can be determined. If certain muscles do not respond to aging then it seems a waste of resources t o do so, and other methods of ensuring tenderness need to be explored. If muscles from the chuck and round do respond to aging, then targeting or customizing aging time to individual muscles and desired level of tenderness would seem appropriate. Material s and Methods Institutional Meat Purchase Specifications (IMPS) (North American Meat Processors, 1988) 115 2 piece boneless chucks and IMPS 167A peeled knuckles were purchased from a major packer of known USDA grade and slaughter date. Two grades of cuts were studied: USDA Select and the upper 2/3 of the USDA Choice grade. Eight subprimals of each grade were immediately shipped to the University of Florida Meats Laboratory for muscle separation. The IMPS 115 2 piece chuck was separated and the following muscles were selected for study: infraspinatus, triceps brachii lateral head, triceps brachii long head, serratus ventralis, complexus, splenius, and rhomboideus. The IMPS 167A knuckle was also separated and the vastus lateralis and rectus femoris wer e evaluated. These nine muscles were selected because of the possibility that these could be used as steak cuts where tenderness is critical due to the probability that they would be cooked with a dry cooking method, based on results from the Muscle Profi ling Study conducted by University of Florida and University of Nebraska in conjunction with National Cattlemans Beef Association (NCBA, 2000). Each muscle was divided into four portions, progressing from anterior to posterior orientation to the carcass, or from dorsal to ventral orientation to the carcass depending

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31 on muscle fiber orientation: A was the 1 st 25% portion of the muscle, B was the 2 nd 25% portion of the muscle, C was the 3 rd 25% portion of the muscle, and D was the 4 th 25% portion of the mus cle. One steak was removed for evaluation from each portion of the muscle to be studied. For small muscles the entire portion may have been used as the steak. Postmortem aging was conducted for 7, 14, 21, or 28 days at 2 2C. Individual steaks were v acuum sealed in Cryovac B550T (Sealed Air Corp., Duncan, SC) bags and subsequently heat shrunk in 82C water as per manufacturers recommendation. A Latin square was used to assign each steak into one of four postmortem aging treatments. There were eight 2 piece chucks from the USDA Select grade numbered one through eight, and eight knuckles from the USDA Select grade numbered one though eight. The same numbering system was used for the subprimals from the USDA Choice grade. For pieces one through four, the postmortem aging period was rotated clockwise for each location. For pieces five through eight, the positions for postmortem aging period was rotated counter clockwise. This was done to remove muscle location effect on WBS values. Also, this treatme nt allocation method allowed for location effect to be tested and determined statistically. After achieving the appropriate postmortem aging treatment, steaks were frozen at 40 C then transferred to a 20 C holding freezer until WBS could be conducted. Eight of each of the subprimals for each grade were sampled and replicated twice for a total of 32 subprimals boned to generate 288 muscles. Four steaks per muscle produced 1152 observations for this trial. Steaks were thawed for 18 hours at 2 to 4 C th en broiled on Farberware (Farberware, Bronx, NY) open hearth broilers to an internal temperature of 71C

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32 (American Meat Science Association, 1995). The housing and drip pans of each broiler were covered with aluminum foil and preheated for 15 min. Copper constantan thermocouples attached to a potentiometer were placed in the approximate geometric center of each steak and used to record internal temperature. Steaks were turned when the internal temperature of 35 C was reached and removed from the broiler when the internal temperature reached 71C. Samples were allowed to cool at 2 to 4 C for approximately 18 hours and then 4 to 6 1.27 cm cores were removed from each steak, parallel to fiber orientation, for shear force determination. Shear force determ inations were conducted on an Instron (Canton, MA) universal testing machine equipped with a WBS head, with a crosshead speed of 200 mm/min. Least squares, fixed model procedures of SAS (2001) were used to analyze these data. This study was analyzed as a split plot design where quality grade and muscle was the main plot and postmortem aging and location were the sub plots which were assigned using a Latin square design. Results and Discussion Mean values and other descriptive statistics are presented in Ta ble 3 1 for the nine muscles evaluated in this study. The results of the current study agree with that of Rhee et al. (2004). For the muscles that were evaluated in both studies, the infraspinatus the most tender muscle, followed by the rectus femoris. Rhee et al. (2004) showed a higher WBS for the triceps brachii than the rectus femoris, where as in the current study, the triceps brachii lateral head and the triceps brachii long head were equivalent in WBS to the rectus femoris. For consumer panel rati ngs, Kukowski et al. (2004) also found the infraspinatus to be the most tender muscle followed by the triceps brachii, the serratus

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33 ventralis, and the complexus, which are comparable to the WBS results obtained in the current study. Table 3 2 gives the m ean and standard deviation for the nine muscles used in this study. The rhomboideus, vastus lateralis, and splenius muscles were the least tender tier of the muscle groups and the infraspinatus muscle was by far the most tender of the nine muscles. The i ntermediate group of muscles that were very similar in WBS included the triceps lateral and long head, complexus, serratus ventralis, and rectus femoris. Variation in shear values appeared to be directly related to average shear value. For instance, the rhomboideus had the highest standard deviation and the highest average WBS value. In comparison, the infraspinatus had the lowest standard deviation and average shear value. The analysis of variance revealed a significant grade by postmortem aging interac tion effect; Table 3 3 gives interaction mean values for these two factors. The USDA Select Grade steaks had a significant reduction in shear force values between 7 and 14 days of about 10 percent. There was no significant reduction of shear values after 14 days. Doty and Pierce (1961) reported that beef from all carcass grades had substantially reduced shear force requirements after two weeks of aging, but further aging did not reduce shear force values. For steaks from the upper two thirds of the Choi ce grade, no significant improvement in WBS values was noted after 7 days postmortem aging. This is similar to results from Smith et al. (1978) which reported that aging beyond 11 days did not accomplish further reductions in shear force requirements, and Mitchell et al. (1991) reported little advantage in extending aging beyond 10 days. The effect of grade was only significant at day 7 and day 21 of postmortem aging (Table 3). If an end user has the ability or can afford to hold steaks for 28 days postm ortem, then

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34 according to these data, USDA Select would be equivalent to the upper two thirds of the Choice grade for WBS force values. There was a significant main effect for USDA Grade and for postmortem aging; these values are also presented in Table 3 3. When averaged across all postmortem aging periods, grade only influenced WBS values by about 5 percent. The grade effect was greatest at 7 days postmortem and lessened as postmortem aging increased. If grade is ignored and only postmortem aging cons idered, it appeared that there was a significant decrease in WBS values between 7 and 14 days aging and 21 and 28 days aging. These data would suggest that 14 days aging would be an appropriate recommendation if end users could not hold product an entire 28 days aging period. This 14 day aging recommendation agrees with that of other researchers (Doty and Pierce, 1961; Eilers et al., 1996; Miller et al., 1997). Miller et al. (1997) suggested that aging beef for 14 days would improve the consistency of be ef tenderness and should be recommended as a processing control point for the beef industry to improve consumer acceptance of beef regardless of breed, fatness, or processing variables. Table 3 4 presents the effect of muscle location on WBS force values b y muscle. Only four of the nine muscles were significantly impacted by anatomical location on shear force values, those included the complexus, rhomboideus, vastus lateralis, and rectus femoris. Both the complexus and rhomboideus muscles had higher shear force values going from the anterior to the posterior portion of the muscle. Both of these muscles run along the top of the shoulder and neck in close proximity. For the complexus, the anterior 25 percentile muscle portion had higher shear value than th e center 50 percent of the muscle. The quartile closest to the wholesale rib was the lowest

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35 in shear value and about 26 percent lower in shear value than the quartile found closest to the head. Similar results were noted for the rhomboideus, except not a s extreme as noted for the complexus. The anterior one half of the muscle was approximately nine percent higher in shear value than the posterior quartile of the muscle. The two muscles evaluated from the knuckle were opposite in location effect when co mpared to the two previously mentioned muscles. Both the vastus lateralis and rectus femoris had increasing shear value when going from the anterior to posterior portion of the muscle. The anterior one half of the vastus lateralis was approximately 10 pe rcent more tender than the posterior quadrant of the muscle from the chuck. The rectus femoris was similar in its aging pattern to the vastus lateralis muscle in that the anterior 25 percent was more tender than the posterior 25 percent of the muscle. Th e middle 50 percent of the muscle was intermediate in shear values to the two end quadrants and not statistically different. Reuter et al. (2002) found a tenderness variation within the biceps femoris and the semimembranosus, but not within the adductor an d the semitendinosus. For the biceps femoris and the semimembranosus the lowest shear force values were at the anterior end, highest shear force values at the posterior end and intermediate shear values in the middle (Reuter et al. 2002), which is similar to the rectus femoris in the current study. These data would suggest that for at least some individual muscles of the chuck and round, location should be considered when fabricating and merchandizing these muscles. For other muscles, location within the muscle need not be considered when merchandizing decisions are made. Postmortem aging affects by muscle interaction was tested within subprimals and found to be not significant (P = 0.53). This suggests that postmortem aging affects all

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36 muscles in a sim ilar manner for WBS force values. Therefore, aging recommendations for the nine muscles studied in this project can be identical but USDA grade or intramuscular fat content would need to be considered. In contrast, Parrish et al. (1991) reported that there was no difference between the aging rates of USDA Choice versus USDA Select longissimus, but aging rates were significantly influenced by USDA quality grade. Steaks that graded Choice had lower WBS values than Prime or Select steaks (Parrish et al. 1991) It is important to note that there was a greater difference in grade or intramuscular fat in the present study because the Select grade was compared to the upper two thirds of the Choice grade. Parrish (1997) noted that tenderloin and eye of round had different aging patterns from the longissimus muscle whereas muscles in the present study appeared to age in a similar fashion. It is important to note also that in the Parrish study, muscles of locomotion were compared to muscles of support where in the p resent study all muscles would be considered locomotive muscles. Miller et al. (1997) reported that sensory scores for USDA Choice steaks were higher than USDA Select, but USDA quality grade did not affect WBS. Kukowski et al. (2004) also reported USDA C hoice steaks to have higher sensory panel scores than USDA Select steaks, but did not test WBS. Implications Postmortem aging affects all of the muscles evaluated in this study in a similar fashion. Therefore, consistent recommendations about postmortem a ging can be given for these muscles. This study revealed that USDA grade would have an effect on postmortem aging, in that for muscles from the upper two thirds of USDA Choice grade was not significantly improved after seven days postmortem aging. Muscle s from the

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37 USDA Select grade should be aged a minimum of 14 days postmortem to achieve optimum tenderness. Location within a muscle was found to have an effect on WBS values in four of the nine muscles evaluated. This would indicate that muscles would hav e to be treated on an individual basis when fabrication and merchandising individual retail cuts or portions from muscles of the chuck and round. For some muscles, location within the cut can be ignored and for others location must be considered for tende rness enhancement or product utilization.

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38 Table 3 1. Means, standard deviations, minimum, and maximum values for WBS at 14 days postmortem aging by muscle Subprimal Muscle Mean, kg SD Minimum, kg Maximum, kg Chuck Triceps lateral 3.8 0.66 2.1 5.2 Tric eps long 3.8 0.67 2.5 5.3 Splenius 4.5 0.97 3.0 6.4 Complexus 3.7 0.97 2.3 7.2 Rhomboideus 5.2 1.13 3.3 7.3 Serratus ventralis 3.7 0.78 2.1 5.2 Infraspinatus 2.8 0.58 1.8 4.5 Knuckle Vastus lateralis 4.5 0.96 3.1 7.2 Rectus femoris 3.8 0.78 2. 4 5.5 Each muscles mean represents an average of 768 measurements.

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39 Table 3 2. WBS values for muscles of the chuck and knuckle averaged across all aging periods Subprimal Muscle Mean, kg SD Chuck Triceps lateral head 3.9 d 0.79 Triceps long head 3. 8 de 0.76 Splenius 4.4 c 1.07 Complexus 3.6 e 0.85 Rhomboideus 5.0 a 1.27 Serratus ventralis 3.6 e 0.84 Infraspinatus 2.8 f 0.75 Knuckle Vastus lateralis 4.7b 0.97 Rectus femoris 3.8 de 0.97 abcdef Means with the same superscript in the same column are not significantly different at P<0.05 according to LSD=0.225. Each muscles mean represents an average of 768 measurements.

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40 Table 3 3. WBS values by grade and aging treatment Postmortem aging (days) Grade 7 14 21 28 Average Mean, kg SD Mean, kg S D Mean, kg SD Mean, kg SD Mean, kg SD Select 4.4 ax 1.32 4.0 bx 1.01 4.1 bx 1.15 3.9 bx 0.91 4.1 x 1.12 Top Choice 3.9 ay 1.23 3.9 ax 1.09 3.8 ay 1.05 3.8 ax 1.11 3.9 y 1.12 Average 4.2 a 1.30 4.0 b 1.05 4.0 bc 1.11 3.8 c 1.01 4.0 abc Means with same superscript on same row are not significantly different at P<0.05 according to LSD=0.21 for the individual grades, and LSD=0.15 for the average of the grades. xy Means with same superscript on same column are not significantly different at P<0.05 according to LSD=0.22 for the individual age groups, and LSD=0.18 for the average of all age groups. Each grade mean represents an average of 432 measurements.

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41 Table 3 4. WBS values by location Location A B C D Subprimal Mean, kg SD Mean, kg SD Mean, kg SD Mean, kg SD Chuck Triceps lateral 3.7 a 0.72 3.9 a 0.88 4.0 a 0.74 4.1 a 0.79 Triceps long 3.8 a 0.86 3.8 a 0.78 3.8 a 0.66 4.0 a 0.74 Splenius 4.3 a 1.00 4.5 a 1.07 4.3 a 0.86 4.7 a 1.29 Complexus 4.2 a 1.02 3.7 b 0.75 3.7 b 0.74 3.1 c 0.51 Rhomboideus 5.3 a 1.20 5.2 a 1.37 5.1 ab 1.28 4.8 b 1.21 Serratus ventralis 3.6 a 0.70 3.6 a 0.96 3.5 a 0.64 3.7 a 1.05 Infraspinatus 2.9 a 0.75 2.8 a 0.73 2.7 a 0.82 2.7 a 0.68 Knuckle Vastus lateralis 4.5 b 0.85 4.5 b 0.89 4.8 ab 1.1 5.0 a 1.04 Rectus femoris 3.4 c 0.83 3.8 abc 0.88 3.9 ab 1.12 4.1 a 0.92 abc Means with same superscript in same row are not significantly different at P<0.05 according to LSD=0.45. Each muscle mean is an average of 1,728 measurements.

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42 CHAPTER 4 EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON COOK AND THAW LOSS OF SELECTED MUSCLES OF LOCOMOTION OF THE BEEF CHUCK AND ROUND Introduction Recently, University of Florida and University of Nebraska Scientists characterized thirty seven muscle s of the beef chuck and round relative to size, shape, palatability, and composition (NCBA, 2000). This study revealed that a significant number of these muscles, when removed separately and cut across the grain, were very acceptable in sensory panel scor es. Their conclusions were that there are numerous muscles that could be up graded in value by cutting them into steaks rather than selling them as part of a roast or grinding into ground beef (NCBA, 2000). Kukowski et al. (2004) found the complexus, ser ratus ventralis, triceps brachii, and the infraspinatus were acceptable to consumers as steaks. In recent years, economic pressures have challenged the livestock and meat industries to seek ways of producing meat products that will enable consumers to rec eive maximum palatability benefits at the lowest costs (Morgan et. al., 1991). With traditional roasts cuts being marketed as individual muscle steaks instead of roasts, valued could be added to the beef carcass (Kukowski et al., 2004). The round represe nts approximately 22% of the weight of a typical beef carcass and contains some of the least tender muscles of the carcass (Ramsbottom et al., 1945; Jones et al., 2001). Rhee et al. (2004) found that the adductor, semimembranosus, gluteus medius, and semi tendinosus all from the round; and the supraspinatus from the chuck had high Warner Bratzler shear force values (WBS

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43 = 4.29 kg). Savell and Smith (2000) reported that the chuck represents about 30% of the total carcass weight. That is approximately 52% o f the carcass that is currently used primarily as ground beef and roasts. Miller et al. (2001) found that consumers were willing to pay a premium for steaks that reach certain levels of tenderness. One of the most prevalent and non invasive methods of pos tmortem tenderization is aging meat at refrigerated temperatures (Parrish, 1997). Thaw loss and cook loss could be of concern when aging meat though (Mitchell et al., 1991). However, that study did not report significant differences in thawing or cooki ng losses among aging periods. Rhee et al. (2004) found a lower cooking loss for the biceps femoris in the round than any chuck muscles studied when aged to 14 days. As the industry begins to isolate individual muscles of the chuck and round for merchand ising as steak cuts that will be cooked commonly with a dry cooking method, then more knowledge about how these muscles respond to postmortem aging is required. The economic incentives for the industry to improve the tenderness of beef must be established before significant improvements in the consistency and palatability of beef will occur (Miller et al., 1998). Kukowski et al. (2004) asked panelist to assign a price/0.45 kg (0=would not buy, 10=$10/0.45 kg). Consumers were willing to pay $5.68/0.45 kg f or the infraspinatus, and $5.15/0.45 kg for the triceps brachii. This could provide an incentive for retailers to use these individual muscles as steak cuts. Other cuts from the Kukowski et al. (2004) study that were found to be acceptable as steaks cuts were the serratus ventralis ($4.78/0.45 kg), and the complexus ($4.75/0.45 kg).

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44 According to Miller et al. (1998), the most important factor in a tenderness study with consumers was to establish that a range in beef tenderness from tender to tough exists Continued work is needed on improving meat tenderness, primarily for retail cuts from the round and chuck. If consumers are willing to pay more for guaranteed tender beef products (Boleman et al., 1997), additional work needs to be conducted to investig ate aging patterns of other muscles of the chuck and round so that the highest and best use for each muscle can be determined. And if thaw loss and cook loss is a concern with aging, the cost and benefit of aging versus loss needs to be explored. If cert ain muscles do not respond to aging then it seems a waste of resources to do so, and other methods of ensuring tenderness need to be explored. If muscles from the chuck and round do respond differently to aging, then targeting or customizing aging time to individual muscles and desired level of tenderness would seem appropriate. Materials and Methods Institutional Meat Purchase Specifications (IMPS) (North American Meat Processors, 1988) 115 2 piece boneless chucks and IMPS 167A peeled knuckles were purcha sed from a major packer of known USDA grade and slaughter date. Two grades of cuts were studied: USDA Select and the upper 2/3 of the USDA Choice grade. Eight subprimals of each grade were immediately shipped to the University of Florida Meats Laboratory for muscle separation. The IMPS 115 2 piece chuck was separated and the following muscles were selected for study: infraspinatus, triceps brachii lateral head, triceps brachii long head, serratus ventralis, complexus, splenius, and rhomboideus. The IMPS 167A knuckle was also separated and the vastus lateralis and rectus femoris were evaluated. These nine muscles were selected because of the possibility that these could be used as steak cuts where tenderness is critical due to the probability that th ey

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45 would be cooked with a dry cooking method, based on results from the Muscle Profiling Study conducted by University of Florida and University of Nebraska in conjunction with National Cattlemans Beef Association (NCBA, 2000). Each muscle was divided int o four portions, progressing from anterior to posterior orientation to the carcass, or from dorsal to ventral orientation to the carcass depending on muscle fiber orientation: A was the 1 st 25% portion of the muscle, B was the 2 nd 25% portion of the muscle C was the 3 rd 25% portion of the muscle, and D was the 4 th 25% portion of the muscle. One steak was removed for evaluation from each portion of the muscle to be studied. For small muscles the entire portion may have been used as the steak. Postmortem aging was conducted for 7, 14, 21, or 28 days at 2 2C cooler temperature. Individual steaks were vacuum sealed in Cryovac B550T (Sealed Air Corp., Duncan, SC) bags and subsequently heat shrunk in 82C water as per manufactures recommendation. A Latin square was used to assign each steak into one of four postmortem aging treatments. There were eight 2 piece chucks from the USDA Select grade numbered one through eight, and eight knuckles from the USDA Select grade numbered one though eight. The same nu mbering system was used for the subprimals from the USDA Choice grade. For pieces one through four, the postmortem aging period was rotated clockwise for each location. For pieces five through eight, the positions for postmortem aging period was rotated counter clockwise. This was done to remove muscle location effect. Also, this treatment allocation method allowed for location effect to be tested and determined statistically. After achieving the appropriate postmortem aging treatment, steaks were froze n at 40 C then transferred to a 20 C holding freezer until analysis could be conducted.

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46 Eight of each of the subprimals for each grade were sampled and replicated twice for a total of 32 subprimals boned to generate 288 muscles. Four steaks per muscl e produced 1152 observations for this trial. Steaks were thawed for 18 hours at 2 to 4 C then broiled on Farberware (Farberware, Bronx, NY) open hearth broilers to an internal temperature of 71C (American Meat Science Association, 1995). The housing and drip pans of each broiler were covered with aluminum foil and preheated for 15 min. Copper constantan thermocouples attached to a potentiometer were placed in the approximate geometric center of each steak and used to record internal temperature. Steaks were turned when the internal temperature of 35 C was reached and removed from the broiler when the internal temperature reached 71C. Weight in grams was taken while the steaks were frozen, after thawing, and after cooking for calculation of cook loss and thaw loss. Least squares, fixed model procedures of SAS (2001) were used to analyze these data. This study was analyzed as a split plot design where quality grade and muscle was the main plot and postmortem aging and location were the sub plots which were assigned using a Latin square design. Results and Discussion Thaw loss mean values and standard error means (SEM) are shown in Table 4 1 for the nine muscles averaged across all aging periods. The infraspinatus had the lowest amount of thaw loss, fol lowed by the rectus femoris, splenius. The rhomboideus and the complexus had by far the most thaw loss, with the vastus lateralis and the triceps both lateral and long head being similar. The serratus was intermediate for thaw loss. Compared to Warner B ratzler (WBS) shear force for the same nine muscles, from the previous chapter, the rhomboideus and the vastus lateralis were in the least tender tier of

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47 muscles also. The infraspinatus had both the lowest amount of thaw loss and the lowest WBS. The thaw loss percentage could have an effect on the endpoint tenderness. The aging treatment did not have an effect on thaw loss. The interaction of grade by age is shown in Figure 4 1. As USDA Select grade was aged from 7 to 21 days, there was an increased per centage of thaw loss. However, after 14 to 21 days of age, it seems that there is not further increase in thaw loss percentages. For USDA Choice grade, there was in increase from 14 to 28 days of aging. There is not a difference in thaw loss for steaks from the USDA Choice grade aged from 7 to 14 days. It seems also that by 28 days of aging, there were no significant differences in steaks from either the USDA Choice or the USDA Select grades The splenius and vastus lateralis and triceps brachii lateral head had the largest amount of cook loss as shown in Table 4 2. The triceps brachii long head, the rectus femoris and the infraspinatus followed these muscles. The muscles with the least amount of loss were the serratus ventralis, rhomboideus and the com plexus. The splenius, complexus and rhomboideus had low thaw losses and subsequently higher cook losses as compared to other muscles. Rhee et al. (2004) reported that the infraspinatus and the triceps brachii had low cook losses after 14 days of age. Th is is consistent with the findings of the current study with the exception of the higher cook loss for the triceps brachii lateral head. The analysis of variance revealed a grade by muscle interaction effect (Figure 4 2). The muscles responded differently depending on grade. The most significant cook loss was observed for the triceps brachii lateral head and the serratus ventralis. The explanation of this is not clearly obvious but could be due to the amount of exposed

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48 muscle fibers during the cooking p rocess. The muscle fibers from these steaks run in a fan shaped pattern allowing for more detrimental effects of heat to the fibers. Another possibility is the amount of connective tissue that is located within these muscles. There could be a great cook loss with a higher amount of connective tissue although Mitchell et al. (1991) and Jones et al. (1992) did not observe this difference. This difference may have been seen in the infraspinatus also if the connective tissue had not been trimmed from the mu scle prior to steak separation. All other muscles had less observable losses for both the USDA Select and USDA Choice steaks. The triceps brachii long head and to a less extent, the rhomboideus had a slightly higher cook loss for USDA Choice, but it was n ot significant. Berry and Leddy (1990) observed a lower cooking loss for USDA Select steaks than USDA Choice steaks when the steaks were broiled. This does not agree with the current study where USDA Select had a higher amount of cooking loss than did US DA Choice. The interaction effect of age by subprimal approached a level of significance with P=0.071). This interaction is shown in Figure 4 3. As the chuck was aged from 7 to 28 days, the cook loss tended to increased. With the knuckle, the cook loss tended to decrease from 7 to 14 days of aging and from 21 to 28 days of aging. Cook loss remained consistent from 14 to 21 days of aging. There are more detrimental effects to steaks from the knuckle when they are aged from 14 to 21 days. Rhee et al. (2 004) reported that low biceps femoris cook losses were unique among muscles from the round. It seems that in the current study, there is a larger cook loss associated with muscles from the knuckle.

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49 The majority of researchers have not reported a significa nt difference in cook losses and thaw losses among grade or muscle (Mitchell et al., 1991; Jones et al., 1992; Shackelford et al., 1997) with the exception of higher cook losses when steaks are cooked with a belt grill. Implications There is a greater amo unt of thaw loss and cook loss for steaks from USDA Select than for steaks from USDA Choice grades. Further research needs to be conducted to discover why. Aging USDA Select grade from 14 to 21 days seems to reduce the likelihood that further increases i n thaw loss percentages will occur. For USDA Choice grade there is no differences in thaw loss until after 14 days of postmortem aging. After 28 days of aging there is no difference in thaw loss steaks between the USDA Choice or the USDA Select grades. It is suggested that aging past 14 days will increase thaw loss, but cook loss is possibly only affected by cooking method as suggested by Shackelford et al. 1997).

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50 Table 4 1. Thaw loss for muscles of the chuck and knuckle averaged across all aging period s Subprimal Muscle Mean, % SEM Chuck Triceps lateral head 3.8 cd 0.23 Triceps long head 3.8 bcd 0.23 Splenius 3.2 de 0.23 Complexus 4.9 a 0.23 Rhomboideus 4.5 a 0.23 Serratus ventralis 3.5 cd 0.23 Infraspinatus 2.2 f 0.23 Knuckle Vastus laterali s 4.2 ac 0.23 Rectus femoris 3.1 e 0.23 abcdef Means with the same superscript in the same column are not significantly different at P<0.05. Each muscle mean is an average of 768 measurements.

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51 Table 4 2. Cook loss for muscles of the chuck and knuckle a veraged across all aging periods Subprimal Muscle Mean, % SEM Chuck Triceps lateral head 32.4 ab 0.50 Triceps long head 31.1 bcde 0.50 Splenius 33.6 a 0.51 Complexus 30.8 cde 0.51 Rhomboideus 30.5 de 0.51 Serratus ventralis 30.0 e 0.50 Infraspin atus 30.9 bcd 0.50 Knuckle Vastus lateralis 32.3a b 0.50 Rectus femoris 31.6 bcd 0.50 abcde Means with the same superscript in the same column are not significantly different at P<0.05. Each muscle mean is an average of 768 measurements.

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52 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 7 14 21 28 Aging period, days Thaw loss, % Select Top Choice c ab a abc c c bc abc abc Means with the same superscript are not significantly different at P<0.05. Each grade mean is an average of 864 measurements. Figure 4 1. Thaw loss average for grades across aging periods.

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53 0 5 10 15 20 25 30 35 40 Triceps lateral head Triceps long head Sp lenius Comp lexus Rho mbo ideus Serratus ventralis Infraspinatus Vastus lateralis Rec tus fe mo ris Cook loss, % Select Top Choice gh efg bc ab defg efg a efg fg fg efg bcdefg cdefg bc defg bcde h cdefg abcdegfh Means with the same superscript in the are not significantly different at P<0.05. Each muscle mean at each grade is an average of 384 measurements. Figure 4 2. Cook loss for muscles by grade.

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54 27 28 29 30 31 32 33 34 7 14 21 28 Aging period, days Cook loss % Chuck Knuckle bc ab abc a abc abc c ab abc Means with the same superscript are not significantly different at P<0.05. Each chuck mean is an average of 1,344 measurements. Each knuckle mean is an average of 384 measurements. Figure 4 3. Cook loss of subprimals averaged across grade by aging period.

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55 CHAPTER 5 CONCLUSIONS Postmortem aging affects all of the muscles evaluated in this study in a similar fashion. Therefore, consistent recommendations about postmortem aging can be given for these muscles of locomotion. This study revealed that USDA grade would have an effect on postmortem aging, in that for muscles from the upper two thirds of USDA Choice grade were not significantly improved after seven days postmortem aging. Muscles from the USDA Select grade should be aged a minimum of 14 days postmor tem to achieve optimum tenderness. Location within a muscle was found to have an effect on Warner Bratzler shear values in four of the nine muscles evaluated. This indicated that muscles would have to be treated on an individual basis when fabricating and merchandising individual retail cuts or portions from muscles of the chuck and round. For some muscles, location within the cut can be ignored and for others location must be considered for tenderness enhancement or product utilization. There was a great er amount of thaw loss and cook loss for steaks from USDA Select than for USDA Choice grades. It was not entirely obvious as to why, so further research needs to be conducted. Aging USDA Select grades from 14 to 21 days seems to reduce the likelihood tha t further increases in thaw loss percentages will occur. For USDA Choice grades, there was no difference in thaw loss until 14 days. After 28 days of aging there was no difference in thaw loss of steaks between the USDA Choice and the

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56 USDA Select grades. Aging past 14 days postmortem will increase thaw loss, but cook loss is possibly only affected by cooking method.

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57 LIST OF REFERENCES Alsmeyer, R. L., A. Z. Palmer, M. Koger, and W. G. Kirk. 1959. The relative significance of factors influencing and/or associated with beef tenderness. Proc. 11th Research Conf., Am. Meat Inst. Found. Circ., p. 85. Alsmeyer, R. L., J. W Thornton, and R. L. Hiner. 1965. Some dorsal lateral location tenderness differences in the longissimus dorsi muscle of beef and pork. J. Anim. Sci. 24:526. Alsmeyer, R. L., J. W. Thornton, R. L. Hiner and N. C. Bollinger. 1966. Beef and pork tenderness measured by the press, Warner Bratzler and STE methods. Food Technol. 20:115. American Meat Science Association. 1995. Research guidelines for cookery, sensory evaluation, and instrumental tenderness measurements of fresh meat. Am. Meat Sci. Assoc. and Nat. Live Stock and Meat Board. Berry, B. W., and K. F. Leddy. 1990. Comparison of restaurant vs. research type broiling with beef loin steaks differing in marbling. J. Anim. Sci. 68:666. Boleman, S. J., S. L. Boleman, R. K. Miller, J. F. Taylor, H. R. C ross, T. L. Wheeler, M. Koohmararie, S. D. Shackelford, M. F. Miller, R. L. West, D. D. Johnson, J. W. Savell. 1997. Consumer evaluation of beef of known categories of tenderness. J. Anim. Sci. 75:1521. Blumer, T. N. 1963. Relationship of marbling to the p alatability of beef. J. Anim. Sci. 22:771. Brady, D. E. 1937. A study of the factors influencing tenderness and texture of beef. Proc. Amer. Soc. of Anim. Prod., Dec., p.246. Brooks, J. C., J. B. Belew, D. B. Griffin, B. L. Gwartney, D. S. Hale, W. R. Hen ning, D. D. Johnson, J. B. Morgan, F. C. Parrish, Jr., J. O. Reagan, J. W. Savell. 2000. National Beef Tenderness Survey 1998. J. Anim. Sci. 78:1852. Busch, W. A., D. E. Goll, and F. C. Parrish, Jr. 1972. Molecular properties of postmortem muscle. Isometr ic tension development and decline in bovine, porcine, and rabbit muscle. J. Food Sci. 37: 289. Carpenter, Z. L., G. C. Smith and O. D. Butler. 1972. Assessment of beef tenderness with the Armour Tenderometer. J. Food Sci. 37:126.

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58 Christians, C. J., R. L. Henrickson, R. D. Morrison, D. Chambers, and D. F. Stephens. 1961. Some factors affecting tenderness of beef. J. Anim. Sci. 20 (Suppl 1.):904 (Abstr.) Cover, S., O. D. Butler, and T. C. Cartwright. 1956. The relationship of fatness in yearling steers to ju iciness and tenderness of broiled and braised steaks. J. Anim. Sci. 15:464. Cover, S., and R. L. Hostetler. 1960. An examination of some theories about beef tenderness by using new methods. Texas Agr. Exp. Sta. Bull. 947. Cover, S., R. L. Hostetler, and S. J. Ritchey. 1962. Tenderness of beef IV. Relations of shear force and fiber extensibility to juiciness and six components of tenderness. J. Food Sci. 27:527. Cover, S., G. T. King, and O. D. Butler. 1958. Effect of carcass grades and fatness on tendernes s of meat from steers of known history. Texas Agr. Exp. Sta. Bull. 889. Cridge, A. G., R. Bickerstaffe, R. Cowley, and G. Savage. 1994. Postmortem factors influencing the quality of beef. Proc. Nutr. Soc. N. Z. 19:93. Crouse, J. D., L. K. Theer, and S. C. Seideman. 1989. The measurement of shear force by core location in longissimus dorsi beef steaks from four tenderness groups. J. Food Qual. 11:341. Davey C. L., H. Kuttel and K. V. Gilbert. 1967. Shortening as a factor in meat aging. Food Technol. 2:53. Da yton, W. R., W. J. Reville, D. E. Goll, and M. H. Stormer. 1976. A Ca 2+ activated protease possible involved in myofibrilliar protein turnover: partial characterization of the purified enzyme. Biochemistry. 15:2159. Dikeman, M. E., and J. D. Crouse. 1975. Chemical composition of carcasses from Hereford, Limousin and Simmental crossbred cattle as related to growth and meat palatability. J. Anim. Sci. 40:463. Dolezal, H. G., G. C. Smith, J. W. Savell, and Z. L. Carpenter. 1982. Comparison of subcutaneous fat thickness, marbling and quality grade for predicting palatability of beef. J. Food Sci. 47:397. Doty, D. M., and J. C. Pierce. 1961. Beef muscle characteristics as related to carcass grade, carcass weight, and degree of aging. USDA Tech. Bull. No. 1231. D utson, T. R. 1983. Relationship of pH and temperature to distribution of specific muscle proteins and activity of lysosomal proteinases. J. Food Biochem. 7:223. Dutson, T. R., Hostetler, R. L., and Z. L. Carpenter. 1976. Effect of collagen and sarcomere sh ortening on muscle tenderness. J. Food Sci. 41:863.

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59 Dutson, T. R., G. C. Smith, and Z. L. Carpenter. 1980. Lysosomal enzyme distribution in electrically stimulated ovine muscle. J. Food Sci. 45:1097. Francis, J. J., J. R. Romans, and H. W. Norton. 1977. Co nsumer rating of two beef marbling levels. J. Anim. Sci. 46:67. Eilers, J. D., J. D. Tatum, J. B. Morgan, and G. C. Smith. 1996. Modification of early postmortem muscle pH and use of postmortem aging to improve beef tenderness. J. Anim. Sci. 74:790 798. George, M. H., J. D. Tatum, H. G. Dolezal, J. B. Morgan, J. W. Wise, C. R. Calkins, T. Gordon, J. O. Reagan, G. C. Smith. 1997. Comparison of USDA quality grade with Tendertec for the assessment of beef palatability. J. Anim. Sci. 75:1538. Ginger, B., and C. E. Weir. 1958. Variations in tenderness within three muscles from beef round. Food Res. 23:662. Goll, D. E., A. F. Carlin, L. P. Anderson, A. R. Kline, and M. J. Walter. 1965. Effect of marbling and maturity on beef muscle characteristics. Food Technol. 19:845. Goll, D. E., Y. Otsuka, P. A. Naganis, J. D. Shannon, S. K. Sathe, and M. Muguruma. 1983. Role of muscle proteinases in maintenance of muscle integrity and mass. J. Food Biocem. 7:137. Harris, J. J., R. K. Miller, J. W. Savell, H. R. Cross, and L. J. Ringer. 1992. Evaluation of the tenderness of beef top sirloin steaks. J. Food Sci. 57:6. Harris, J. J., and J. W. Savell. 1993. Impact of carcass maturity on the tenderness of beef from young cattle. Backgrounder (July issue). Department of Animal Sc iences, Texas A & M University, College Station. Harris, P. V., and W. R. Shorthose. 1988. Meat texture. In: R. A. Lawrie (Ed.) Developments in Meat Science 4. pp 245 286. Elsevier Applied Science Publishers, London. Hay, P. P., D. L. Harrison, and G. E. Vail. 1953. Effects of a meat tenderizer on less tender cuts of beef cooked by four methods. Food Technol. 7:217. Henrickson, R. L., and J. H. Mjoseth. 1964. Tenderness of beef in relation to different muscles and age in the animal. J. Anim. Sci. 9:325. Ho stetler, R. L., and S. J. Ritchey. 1964. Effect of coring methods on shear values determined by Warner Bratzler shear. J. Food Sci. 29:681. Huffman K. L., M. F. Miller, L. C. Hoover, C. K. Wu, H. C. Brittin, C. B. Ramsey.1996. Effect of beef tenderness on consumer satisfaction with steaks consumed in the home and restaurant. J. Anim. Sci. 74:91.

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60 Ilian, M. A., J. D. Morton, M. P. Kent, C. E. Le Couteur, J. Hickford, R. Cowley, R. Bickerstaff. 2001. Intermuscular variation in tenderness: Association with the ubiquitous and muscle specific calpains. J. Anim. Sci. 79:122. Jennings, T. G., B. W. Berry, and A. L. Joseph. 1978. Influence of fat thickness, marbling and length of aging on beef palatability and shelf life characteristics. J. Anim. Sci. 46:658. Jeremia h, L. E. 1978. A review of factors affecting meat quality. Tech. Bull. No. 1 Research Station, Lacombe, Alberta, Canada. J eremiah, L. E., Z. L. Carpenter, G. C. Smith, and O. D. Butler. 1970. Beef quality. I. Marbling as an indicator of palatability. Tex as Agr. Exp. Sta. Tech. Rep. No. 22. Johnson, R. C., C. M. Chen, T. S. Muller, W. J. Costello, J. R. Romans, and K. W. Jones.1988. Characterization of the muscles within the beef forequarter. J. Food Sci. 53:1247. Jones, D. K., J. W. Savell, and H. R. Cros s. 1992. Effects of fat trim on the composition of beef retail cuts 3. Cooking yields and fat retention of the separable lean. J. Muscle Foods. 3:73. Jones, S. D., D. E. Burson, and C. R. Calkins. 2001. Muscle Profiling and Bovine Myology (CDROM). Natl. Cattlemen's Beef Assoc., Centennial, CO. Kerth, C. R., J. L. Montgomery, J. L. Lansdell, C. B. Ramsey, M. F. Miller. 2002. Shear gradient in longissimus steaks. J. Anim. Sci. 80:2390. Koohmararie, M. 1995. The biological basis of meat tenderness and potent ial genetic approaches for its control and prediction. Proc. of Recip. Meat Conf. 48:69. Koohmaraie, M., M. E. Doumit, T. L. Wheeler. 1996. Meat toughening does not occur when rigor shortening is prevented. J. Anim. Sci. 74:2935. Koohmaraie, M., J. E. Scho llmeyer, and T. R. Dutson. 1986. Effect of low calcium requiring calcium activated factor on myofibrils under varying pH and temperature conditions. J. Food Sci 51:28. Koohmaraie, M., S. C. Seideman, J. E. Schollmeyer, T. R. Dutson, and A. S. Babiker. 1988 Factors associated with the tenderness of three bovine muscles. J. Food Sci. 53:407. Koohmaraie, M., S. C. Seideman, J. E. Schollmeyer, T. R. Dutson, and J. D. Crouse. 1987. Effect of postmortem storage on Ca ++ dependent proteases, their inhibitor and my ofibril fragmentation. Meat Sci. 19:187. Kopp, J. and C. Vanlin. 1980 81. Can muscle lysosomal enzymes affect muscle collagen postmortem? Meat Sci. 5:319.

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61 Kropf, D. H., and R. L. Graf. 1959. Inter relationships of subjective, chemical and sensory evaluatio ns of beef quality. Food Technol. 13:492. Kukowski, A. C., R. J. Maddock, and D. M. Wulf. 2004. Evaluating consumer acceptability of various muscles from the beef chuck and rib. J. Anim. Sci. 82:521 525. Locker, R. H. 1960. Degree of muscular contraction a s a factor in the tenderness of beef. Food Res. 25:304. Locker, R. H. 1985. Cold induced toughness in meat. In: Advances in Meat Research Vol. 1, pp. 1 44, Pearson, A. M.; Dutson, T. R. (Eds.). AVI Publishing Co., Inc. Westport, CT. Lorenzen, C. L., R. K. Miller, J. F. Taylor, T. R. Neely, J. D. Tatum, J. W. Wise, M. J. Buyck, J. O. Reagan, and J. W. Savell. 2003. Beef Consumer Satisfaction: Trained sensory panel ratings and Warner Bratzler shear force values. J. Anim. Sci. 81:143. Lorenzen, C. L., B. H. W eatherly, and J. W. Savell. 1998. Determination of an aging index. A final report to the Texas Beef Council, Austin, from the Meat Science Section, Department of Animal Science, Texas A&M University, College Station. Luchak, G. L., R. K. Miller, D. S. Hale and H. R. Cross. 1990. Determination of sensory, chemical and cooking characteristics of USDA Choice and USDA Select retail beef cuts. Am. Meat Sci. Assoc. Proc. Recip. Meat Conf. 43:172 (Abstr.) McBee, Jr., J. L. and J. A. Wiles. 1967. Influence of marb ling and carcass grade on the physical and chemical characteristics of beef. J. Anim. Sci. 26:701. McKeith, F. K., D. L. DeVol, R. S. Miles, P. J. Bechtel, and T. R. Carr. 1985. Chemical and sensory properties of thirteen major beef muscles. J. Food Sci. 5 0:869. Mellgren, R L. 1980. Canine cardiac calcium dependent proteases: Resolution of two forms with different requirement for calcium. FEBS Letters 109:129. Miller, M. F., M. A. Carr, C. B. Ramsey, K. L. Crockett, and L. C. Hoover. 2001. Consumer threshol ds for establishing the value of beef tenderness. J. Anim. Sci. 79:3062. Miller, M. F., L. C. Hoover, K. D. Cook, A. L., Guerra, K. L. Huffman, K. S. Tinney, C. B. Ramsey, H. C. Brittin, L. M. Huffman. 1995. Consumer acceptability of beef steak tenderness in the home and restaurant. J. Food Sci. 60:963. Miller, M. F., C. R. Kerth, J. W. Wise, J. L. Lansdell, J. E. Stowell, and C. B. Ramsey. 1997. Slaughter plant location, USDA quality grade, external fat thickness, and aging time effects on sensory characte ristics of beef loin strip steak. J. Anim. Sci. 75:662.

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62 Miller, M. F., C. B. Ramsey, L. C. Hoover, M. A. Carr, K. L. Crockett. 1998. Consumer thresholds for establishing the value of beef tenderness. RMC Proceedings. 51:4. Mitchell, G. E., J. E. Giles, S. A. Rogers, L. T. Tan, R. J. Naidoo, and D. M. Ferguson. 1991. Tenderizing, ageing, and thawing effect on sensory, chemical, and physical properties of beef steaks. J. Food. Sci. 56:1125 1129. Morgan, J. B., J. W. Savell, D. S. Hale, R. K. Miller, D. B. Gri ffin, H. R. Cross, S. D. Shackelford. 1991. National Beef Tenderness Survey. J. Anim. Sci. 69:3274. North American Meat Processors. 1988. The Meat Buyers Guide. National Association of Meat Purveyors. McLean, VA. National Cattlemen's Association. 1994. Na tional Beef Tenderness Symposium, Executive Summary. April 22 23, 1994, Denver, CO. National Cattlemen's Association, Englewood, CO. Nauman, H. D., C. Braschler, M. Mangel, and V. J. Rhodes. 1961. Consumer and laboratory panel evaluation of Select and Cho ice beef loins. Mo. Agric. Exp. Sta. Res. Bull. 777. National Cattlemens Beef Association (NCBA). 2000. Beef value cuts: New Cuts for the consumer. National Cattlemens Beef Association, Englewood, CO. Neely, T. R., C. L. Lorenzen, R. K. Miller, J. D. Tatum, J. W. Wise, J. F. Taylor, M. J. Buyck, J. O. Reagan, J. W. Savell. 1998. Beef Customer Satisfaction: Role of cut, USDA quality grade, and city on in home consumer ratings. J. Anim. Sci. 76:1027. Olson, D. G., and F. C. Parrish, Jr., W. R. Dayton, a nd D. E. Goll. 1977. Effect of postmortem storage and calcium activated factor on the myofibrilliar proteins of bovine skeletal muscle. J. Food Sci.42:506. Ouali, A., and A. Talmant. 1990. Calpains and calpastatin distribution in bovine porcine, and ovin e skeletal muscles. Meat Sci. 28:331. Palmer, A. Z., J. W. Carpenter, R. L. Alsmeyer, H. L. Chapman, and W. G. Kirk. 1958. Simple correlations between carcass grade, marbling, ether extract of loin eye and beef tenderness. J. Anim. Sci. 17:1153 (Abstr.). P arrish, Jr., F. C. 1974. Relationship of marbling to meat tenderness. Proc. Meat Ind. Res. Conf. p.117. Parrish, F. C., Jr. 1997. Beef Facts: Meat Science. Aging of beef. Nat. Cattlemens Beef Assoc. Fact sheet. FS/MS011. Parrish, Jr., F. C., J. A. Boles, R. E. Rust, and D. G. Olson. 1991. Dry and wet aging effects on palatability attributes of beef loin and rib steaks from three quality grades. J. Food Sci. 56:601.

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63 Parrish, Jr., F. C., D. G. Olson, B. E. Miner, and R. E. Rust. 1973. Effect of degree of mar bling and internal temperature of doneness on beef rib steaks. J. Anim. Sci. 37:430. Pearson, A. M. 1963. Objective and subjective measurements for meat tenderness. Proc. Meat Tenderness Sym. Campbell Soup Co., Camden, NJ, p. 135. Pearson, A. M. 1966. Desi rability of beef its characteristics and their measurement. J. Anim. Sci. 25:843. Pearson, A. M., A. M. Wolzak, and J. I. Gray. 1983. Possible role of muscle proteins in flavor and tenderness of meat. J. Food Biochem. 7:189. Platter, W. J., J. D. Tatum, K. E. Belk, P. L. Chapman, J. A. Scanga, and G. C. Smith. 2003. Relationships of consumer sensory ratings, marbling score, and shear force value to consumer acceptance of beef strip loin steaks. J. Anim. Sci. 81:2741. Ramsbottom, J. M., and E. J. Strandine 1948. Comparative tenderness and identification of muscles in wholesale beef cuts. Food Res. 13:315. Ramsbottom, J. M., E. J. Strandine, and C. H. Koonz. 1945. Comparative tenderness of representative beef muscles. Food Res. 10:497 509. Reuter, B. J., D. M. Wulf, R .J Maddock. 2002. Mapping intramuscular tenderness variation in four major muscles of the beef round J. of Anim. Sci. 80:2594. Rhee, M. S., T. L. Wheeler, S. D. Shackelford, and M. Koohmaraie. 2004. Variation in palatability and biochemical tra its within and among eleven beef muscles. J. Anim. Sci. 80:534 550. Romans, J. R., H. J. Tumam and W. L. Tucker. 1965. Influence of carcass maturity and marbling on the physical and chemical characteristics of beef. J. Anim. Sci. 24:681. SAS. 2001. SAS Use rs Guide: Statistics. SAS Inst., Inc., Cary, NC. Savell, J. W., R. E. Branson, H. R. Cross, D M. Stiffler, J. W. Wise, D. B. Griffin, and G. C. Smith. 1987. National Consumer Retail Beef Study: Palatability evaluation of beef loin steaks that differed in marbling. J. Food Sci. 52:517. Savell, J. W., H. R. Cross, J. J. Francis, J. W. Wise, D. S. Hale, D. L. Wilkes, and G. C. Smith. 1989. National Consumer Retail Beef Study: Interaction of trim level, price and grade on consumer acceptance of beef steaks and roasts. J. Food Qual. 12:251. Savell, J. W., and S. D. Shackelford. 1992. Significance of tenderness to the meat industry. Proc. Recip. Meat Conf. 45:43. Savell, J.W., and G.C. Smith. 2000. Laboratory Manual for Meat Science. 7 th ed. American Press, Bosto n, MA.

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64 Shackelford, S. D., M. Koohmaraie, M. F. Miller, J. D. Crouse, and J. O. Reagan. 1991a. An evaluation of tenderness of the longissimus muscle of Angus by Hereford versus Brahman crossbred heifers. J. Anim. Sci. 69: 171 177. Shackelford, S. D., J. B. Morgan, J. W. Savell, and H. R. Cross. 1991b. Identification of threshold levels for Warner Bratzler shear force in beef top loin steaks. J. Muscle Foods. 2:289. Shackelford, S. D., T. L Wheeler, M. Koohmaraie. 1995. Relationship between shear force and trained sensory panel tenderness ratings of 10 major muscles for Bos indicus and Bos taurus cattle. J. Anim. Sci. 73:3333. Shackelford, S. D., T. L. Wheeler, M. Koohmaraie. 1997a. Tenderness classification of beef: I. Evaluation of beef longissimus shear f orce at 1 or 2 days postmortem as a predictor of aged beef tenderness. J. Anim. Sci. 75:2417. Shackelford, S. D., T. L. Wheeler, M. Koohmaraie. 1997b. Repeatability of tenderness measurements in beef round muscles. J. Anim. Sci. 75:2411. Shackelford, S. D. T. L. Wheeler, M. Koohmaraie 1999. Tenderness classification of beef: II. Design and analysis of a system to measure beef longissimus shear force under commercial processing conditions. J. Anim. Sci. 77:1474. Sharrah, N., M. S. Kunze, and R. M. Pangborn. 1965. Beef tenderness: Comparison of sensory methods with the Warner Bratzler and L.E.E. Kramer shear presses. Food Technol. 19:238. Shorthose, W. R., and P. V. Harris. 1990. Effect of animal age on the tenderness of selected beef muscles. J. Food Sci. 55 :1. Slanger, W. D., M. J. Marchello, R. B. Danielson, C. N. Haugse, V. K. Johnson, A. S. Vidal, W. E. Dinusson, and P. T. Berg. 1985. Muscle tenderness, other carcass traits and the effect of cross breeding on these traits in beef cattle. J. Anim. Sci. 61: 1402. Smith, G. C. and Z. L. Carpenter. 1974. Eating quality of meat animal products and their fat content. National Academy Press, Washington D.C Smith, G. C., Z. L. Carpenter, H R. Cross, C. E. Murphey, H. C. Abraham, J. W. Savell, G. W. Davis, B. W. Berry, F. C. Parrish, Jr. 1984. Relationship of USDA marbling groups to palatability of cooked beef. J. Food Qual. 7:289. Smith, G. C., Z. L., Carpenter, and G. T. King. 1969. Considerations for beef tenderness evaluations. J. Food Sci. 34:612. Smith, G. C., G. R. Culp, and Z. L. Carpenter. 1978. Postmortem aging of beef carcasses. J. Food Sci. 43:823.

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65 Smith, G. C., H. G. Dolezal, and J. W. Savell. 1995. The Final Report of the National Beef Quality Audit -1995. Colorado State Univ., Fort Collins; Oklahom a State Univ., Stillwater; and Texas A&M Univ., College Station. Smith, G. C., J. W. Savell, R. P. Clayton, T. G. Field, D. B. Griffin, D. S. Hale, M. F. Miller, T. H. Montgomery, J. B. Morgan, J. D. Tatum, J. W. Wise, D. L. Wilkes, and C. D. Lambert. 1992 Improving the consistency and competitiveness of beef. The Final Report of the National Beef Quality Audit 1991. pp 1 237. Smith, G. C., J. W. Savell, H. R. Cross, Z. L. Carpenter, C. E. Murphey, G. W. Davis, H. C. Abraham, F. C. Parrish, Jr., and B. W. Berry. 1987. Relationship of USDA quality grades to palatability of cooked beef. J. Food Qual. 10:269. Tuma, H. J., R. L. Henrickson, D. F. Stephens, and R. Moore. 1962. Influence of marbling and animal age on factors associated with beef quality. J. Anim Sci. 21:848. Tuma, H, J., R. L. Henrickson, G. V. Odell, and D. F. Stephens. 1963. Variation in the physical and chemical characteristics of the longissimus dorsi muscle from animals differing in age. J. Anim. Sci. 22:354. Walter, M. J., D. E. Goll, L. P Anderson, and E. A. Kline. 1963. Effect of marbling and maturity on beef tenderness. J. Anim. Sci. 23:1115. Walter, M. J., D. E. Goll, E. A. Kline, L. P. Anderson, and A. F. Carlin. 1965. Effect of marbling and maturity on beef muscle characteristics. Fo od Technol. May 159. Webb, N. B., O. J. Kahlenberg, and H. D. Naumann. 1964. Factors influencing beef tenderness. J. Anim. Sci. 23:1027. Wellington, G. H., and J. R. Stouffer. 1959. Beef marbling, its estimation and influence on tenderness and juiciness. C ornell Univ. Agr. Exp. Sta. Bull. 941. Wheeler, T. L., and Koohmaraie, M. 1994. Prerigor and postrigor changes in tenderness of ovine longissimus muscle. J. Anim. Sci. 72:1232. Wheeler, T. L., L. V. Cundiff, R. M. Koch. 1994. Effect of marbling degree on b eef palatability in Bos taurus and Bos indicus cattle. J. Anim. Sci. 72:3145. Wheeler, T. L., S. D. Shackelford, M. Koohmaraie. 1999. Tenderness classification of beef: IV. Effect of USDA quality grade on the palatability of tender beef longissimus when co oked well done. J. Anim. Sci. 77:882. Wu, J. J., T. R. Dutson, and Z. L. Carpenter. 1981. Effect of postmortem time and temperature on the release of cytosomal enzymes and their possible effect on bovine connective tissue components of muscle. J. Food Sci. 46: 1 132.

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66 BIOGRAPHICAL SKETCH Christy Lynn Greenhaw Bratcher was born in Huntsville, Alabama on October 23, 1979. She spent the first 11 years of life in a small town in North Alabama called Arab. In 1991, she moved to Daytona Beach, Florida, with her parents and brother. After high school, Christy attended the University of Florida pursuing a degree in animal sciences to ultimately become a large animal veterinarian. During the first two years of college, she became interested in meat sciences and specialized h er animal sciences degree by pursuing the option of food safety and meats processing. During her undergraduate program, Christy was involved with Gator Collegiate Cattlewomen and Alpha Zeta, as well as holding a job as a veterinarian technician and then a n assistant at the University of Florida Meat Processing Center, and did an internship with Buckhead Beef in Atlanta, Georgia, for 3 months. This internship became a part time position for her as she finished her Bachelor of Science degree. She also beca me the teaching assistant for ANS 2002, The Meat We Eat, from Fall 2001 to Spring 2002. These experiences guided Christy to pursue a Master of Science degree in animal sciences, after graduating with a Bachelor of Science degree in Spring of 2002. Also, w hile pursuing her undergraduate degree, Christy was married to Michael Bratcher in May of 1999. Michael was pursuing a degree at the University of Florida in exercise and sport sciences with the goal of becoming a physical education teacher and football c oach.

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67 In August 2002, Christy was accepted to a graduate research and teaching program at the University of Florida Department of Animal Sciences under the direction of Dr. W. Dwain Johnson. Her major responsibility during the program was to teach ANS 200 2, The Meat We Eat, and to assist with other meat science undergraduate courses. In the 2003 2004 school year Christy was the recipient of the Jack Fry Graduate Teaching Award for the College of Agricultural and Life Sciences. As a graduate student she w as involved with the Animal Sciences Graduate Student Association and the Graduate Student Council.


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Title: The Effects of Quality Grade, Aging and Location on Selected Muscles of Locomotion of the Beef Chuck and Round
Physical Description: Mixed Material
Copyright Date: 2008

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THE EFFECTS OF QUALITY GRADE,
AGING AND LOCATION ON SELECTED MUSCLES
OF LOCOMOTION OF THE BEEF CHUCK AND ROUND















By

CHRISTY LYNN GREENHAW BRATCHER


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2004

































Copyright 2004

by

Christy Lynn Greenhaw Bratcher















ACKNOWLEDGMENTS

First and foremost I want to thank God for bringing me to this point in my life.

Without my trust in Him, I would have never made it here considering all that I have

dealt with for the last two years. So to God be my glory.

I would also like to thank my husband, Mike, for all the support he has given me

not only throughout my graduate program, but also through my undergraduate program

and in everything else I have attempted. Unfortunately, he missed out on being here for

the most part of my master's program, as he was in Iraq serving our great United States

of America. He is a hero to all. He spent thirteen months away from home and still

managed to lend support through his words the entire time he was away. I am also so

proud of him for completing his bachelor's degree in exercise and sports science this

spring after being out of school for three and a half semesters.

I also owe great gratitude to all of my friends who have brought me through this

time of my life. There are a number of people who have been there for me, and I would

like to thank them all: Deke Alkire, Liz Johnson, Nathan and Wimberley Krueger, Alex

Stelzleni, Davin Harms, Ben Butler, Paul Davis, and also my friends and co-workers in

the University of Florida Meats Processing Center: Byron Davis and Tommy Estevez.

The Meat Processing Center manager, Larry Eubanks, and his wife, Kathleen, who

have been my family away from home throughout my school career, both receive my

debt of gratitude. Larry interested me in attending graduate school and has lent support

in numerous ways to Mike and me since we have known him. I also owe a thank you to









Dr. Dwain Johnson for his guidance and support and extreme patience throughout my

degree, and to the rest of my committee: Drs. Sally K. Williams and Ronald H. Schmidt.

Last but most definitely not least, I would like to extend my gratitude to my

brother, Michael; my grandparents, Glenn and Lutherene Greenhaw and H.C. and the late

Faye Childers; close family friends Phil and Jeanette Carter; and the rest of my family

and Mike's family. But most of all, I would like to thank my parents, Walter and Glenda

Greenhaw, who have lent undying love and support to me for my life and school career.

They have been my strongest supporting foundation and my biggest fans. I am forever

indebted to them for all they have done for me.
















TABLE OF CONTENTS

page

A C K N O W L E D G M E N T S ................................................................................................. iii

LIST OF TABLES ............. .. ................... ...................... .... ...... ............ vii

LIST OF FIGURES ...................................... ..... .. .......... ............ .. viii

A B S T R A C T ............... ................................................................................. ......... ..... ix

CHAPTER

1 IN TRODU CTION ................................................. ...... .................

2 REVIEW OF LITERATURE ......................................................... .............. 3

T enderness .......................... ...... ........... ....................... ... ........ 3
Factors Affecting the Tenderness of Beef ........................................................5
M easurem ent of Tenderness........................................................ ............... 6
A g in g ................................................................................ 10
M echanism of Aging .................. ................................ .. .. .............. .. 11
L length of A going ........................... .................................... .......... ................. .... 13
R ate of M uscle A going ........................................................................... ...... 15
Q quality G rade................................ ............................. ... ......... ............... 17
Association of Level of Marbling and Quality Grade to Tenderness.................. 18
The "Insurance Theory" ............................ ..... ...................................... 20
Differences Detected by Consum ers ....................................... ............... 21
L o catio n ...................................... ......................................................2 3


3 THE EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON WBS
FORCE VALUES ON SELECTED MUSCLES OF LOCOMOTION OF THE BEEF
C H U C K A N D R O U N D .................................................................. .....................27

Intro du action ...................................... ................................................ 2 7
M materials and M methods ...................................................................... ...................30
R results and D discussion ........................ ................ ................... .. ...... 32
Im p location s ........................................................................... 3 6









4 EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON COOK AND
THAW LOSS OF SELECTED MUSCLES OF LOCOMOTION OF THE BEEF
C H U C K A N D R O U N D .................................................................. .....................42

In tro du ctio n ...................................... ................................................ 4 2
M materials and M methods ....................................................................... ..................44
R results and D discussion ...................... .................. ................... .. ...... 46
Im p location s ........................................................................... 4 9


5 CON CLU SION S .................................. .. .......... .. ............55

L IST O F R E FE R E N C E S ..................................................................... ..... ...................57

BIOGRAPHICAL SKETCH ...................................................................66
















LIST OF TABLES

Table p

3-1. Means, standard deviations, minimum, and maximum values for WBS at 14 days
postm ortem aging by m uscle......................................................... ............... 38

3-2. WBS values for muscles of the chuck and knuckle averaged across all aging
p erio d s ............................................................................. 3 9

3-3. W BS values by grade and aging treatment...................................... ............... 40

3-4. W B S values by location ................................................. ................................ 41

4-1. Thaw loss for muscles of the chuck and knuckle averaged across all aging
p erio d s ............................................................................... 5 0

4-2. Cook loss for muscles of the chuck and knuckle averaged across all aging
periods ............................................................... ...... ..... ......... 51
















LIST OF FIGURES


Figure pge

4-1. Thaw loss average for grades across aging periods .............................................52

4-2. Cook loss for m uscles by grade ........................................ ........................... 53

4-3. Cook loss of subprimals averaged across grade by aging period............................54















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

THE EFFECTS OF QUALITY GRADE, AGING AND LOCATION ON SELECTED
MUSCLES OF LOCOMOTION OF THE BEEF CHUCK AND ROUND

By

Christy Lynn Greenhaw Bratcher

May 2004

Chair: D. D. Johnson
Major Department: of Animal Sciences

The objective of this study was to determine the aging patterns of nine selected

muscles from the chuck and round from two quality grades of beef: United States

Department of Agriculture (USDA) Select and the upper 2/3 of USDA Choice grade.

The International Meat Purchase Specifications (IMPS) (NAMP, 1988) 115 2-piece

chuck was separated and the following muscles were selected for study: infraspinatus,

triceps brachii lateral head, triceps brachii long head, serratus ventralis, complexus,

splenius, and rhomboideus. The IMPS 167A knuckle was also separated and the vastus

lateralis and rectus femoris were evaluated. These muscles were selected because of the

possibility of being used as cuts where tenderness is critical due to the probability that

they would be cooked with a dry cooking method, based on results from the Muscle

Profiling Study conducted by the University of Florida and University of Nebraska in

conjunction with the National Cattleman's Beef Association. Each muscle was divided

into four portions, progressing from anterior to posterior or dorsal to ventral orientation to









the carcass. One steak was removed from each portion for evaluation. Aging was

conducted at 7, 14, 21, or 28 days. After achieving their appropriate aging treatment,

Warner-Bratzler Shear (WBS) force analyses were conducted on an Instron (Canton,

MA) universal testing machine. Aging affected all of the muscles evaluated in this study

in a similar fashion; therefore, consistent recommendations can be given for these

muscles. This study revealed that USDA grade had an effect on aging, in that it would

not be necessary to hold muscles from the upper 2/3 of USDA Choice grade beyond 7

days of age. For USDA Choice grade, there was in increase in thaw loss from 14 to 28

days of aging, but aging up to 7 days had no effect. Muscles from lower marbled grades

(i.e., USDA Select), should be aged a minimum of 14 days postmortem. As USDA

Select grade was aged from 7 to 21 days, there was an increased percentage of thaw loss.

However, after 14 to 21 days of age, it seems that there is no further increase in thaw loss

percentages. The muscles respond differently depending on grade; USDA Select

generally had higher cooking losses than USDA Choice. Location within a muscle had

an effect on WBS values in four of the nine muscles evaluated. This indicated that

muscles would have to be treated on an individual basis when fabricating and

merchandising individual retail cuts from these muscles. For some muscles, location

within the cut can be ignored, and for others location must be considered for tenderness

enhancement or product utilization.














CHAPTER 1
INTRODUCTION

In recent years, economic pressures have challenged the livestock and meat

industries to seek ways of producing meat products that will enable consumers to receive

maximum palatability benefits at the lowest costs (Morgan et al., 1991). Due to

consumer demand for smaller portion sizes, beef retailers have been forced to fabricate

steaks from cuts of meat (round and chuck subprimals) that previously were

merchandised solely as roasts (Shackelford et al., 1995). As the industry begins to isolate

individual muscles of the chuck and round for merchandising as steak cuts, then more

knowledge about how these muscles respond to postmortem aging is required in order to

assure tenderness. The round represents approximately 22% of the weight of a typical

beef carcass and contains some of the least tender muscles of the carcass (Ramsbottom et

al., 1945; Jones et al., 2001). Savell and Smith (2000) reported that the chuck represents

about 30% of the total carcass weight. Therefore, approximately 52% of the carcass that

is currently used primarily as ground beef and roasts.

The 1991 National Beef Tenderness Survey (Morgan et al., 1991) revealed

problems with tenderness of beef from the chuck and round subprimals and with the top

sirloin steak. The survey also found that round and chuck cuts were especially tough

despite being cooked by moist-heat methods. Steaks from the round and the chuck were

much tougher than their roast counterparts. The mean shear force of the top round roast

was 4.06 kg while the steak counterpart had an average shear force value of 5.23 kg









(Savell and Shackelford, 1992). The industry must discover a way to utilize these cuts to

provide for optimal utilization of the carcass while ensuring a tender cut of meat.

The economic incentives for the industry to improve the tenderness of beef must be

established before significant improvements in the consistency and palatability of beef

will occur (Miller et al., 1998). According to Miller et al. (1998), the most important

factor in a tenderness study with consumers is to establish that a range in beef tenderness

from tender to tough exists. The range given in Miller et al. (1995) is greater than 2.0

and less than 7.0 kg of shear force. Research has shown that consumers can detect

changes in tenderness similar to those found with instrumental measurements such as

Warner-Bratzler shear force (WBS) (Shackelford et al., 1991b; Miller et al., 1995;

Boleman et al., 1997). Therefore, WBS values can be used as an indicator of the value

relationship for tenderness.

Some possible factors that affect tenderness have been identified as postmortem

storage time and temperature (aging) (Smith et al., 1978; Mitchell et al., 1991; Eilers et

al., 1996;), the quality grade of the carcass (Goll et al., 1965; McBee and Wiles, 1967;

Smith and Carpenter, 1974), and a possible location effect within individual muscles

(Kerth et al., 2002; Reuter et al., 2002; Rhee et al., 2004). Continued work is needed on

improving meat tenderness, primarily for retail cuts from the round and chuck. It is

necessary to get and increased percentage of steaks from the carcass or increase the

percentage of muscles that can be used for steak cuts. If consumers are willing to pay

more for guaranteed tender beef products (Boleman et al., 1997; Kukowski et al., 2004),

it is the industry's job to discover innovative ideas to produce guaranteed tender beef.














CHAPTER 2
REVIEW OF LITERATURE

Tenderness

Consumers have ranked tenderness as being the most important factor influencing

satisfaction (Savell et al., 1987, 1989; Smith et al., 1987). The final report of the 1995

National Beef Quality Audit listed low overall palatability and inadequate tenderness

among the top 10 concerns of the beef industry (Smith et al., 1995). In addition, during

the National Beef Tenderness Symposium (National Cattlemen's Association, 1994) it

was revealed that 1) one in every four steaks is less than desirable in tenderness and

overall palatability (Smith et al., 1992), 2) one tough carcass may affect as many as 542

consumers (Harris and Savell, 1993), and 3) beef industry leadership is adamant about

increasing market-share, with increasing beef tenderness being the key to this change in

positioning (George et al., 1997).

The 1998 National Beef Tenderness Survey (Brooks et al., 2000) collected samples

from 56 retail stores representing 15 retail chains and 14 foodservice facilities in eight U.

S. cities. Steaks were divided into the following quality groups for statistical analysis:

Prime, Top Choice, Choice, Select, and Lean or No Roll. Average postfabrication aging

times were 32 days for foodservice subprimals and 19 days for retail cut samples. The

percentages of retail top round, eye of round, and bottom round steaks with a Wamer-

Bratzler shear (WBS) force of greater than 3.9 kg, the 68% confidence level of

Shackelford et al. (1991b), were 39.5, 55.9, and 68.0, respectively. These data indicate

that improvements in the tenderness of retail cuts from the round are needed. Quality









group had little or no effect on consumer sensory evaluations and WBS values of retail

and foodservice steaks used in this study.

Consumers can differentiate among steaks varying in WBS (Miller et al., 1995;

Huffman et al., 1996). As WBS decreased, tenderness scores increased, indicating that

consumers could detect changes in tenderness similar to those found in instrumental

measurement (Miller et al., 1998). Consumers are also willing to pay more for steaks that

reach a certain level of tenderness (Miller et al., 2001). If there is a possibility of

increasing tenderness in these cuts of beef, the value of the total carcass can be increased.

Boleman et al. (1997) also suggested that consumers can discern between categories of

tenderness and are willing to pay a premium for improved tenderness. In this study, strip

loins were cut into 2.54 cm-thick steaks, and the center steak from each strip loin was

used to determine WBS. The remaining steaks were placed into one of the following

categories based on that WBS and color-coded accordingly: 1) 2.27 to 3.58 kg (Red); 2)

4.08 to 5.40 kg (White); and 3) 5.90 to 7.21 kg (Blue). A $1.10/ kg price difference was

placed between each category and randomly recruited consumers were allowed to

evaluate steaks and purchase them based on their findings. Consumers gave higher

tenderness ratings to Red steaks than to Blue steaks. Overall satisfaction was higher

(P<0.05) for Red steaks than for the other two categories. The following percentages of

steaks were purchased: 1) Red, 94.6%; 2) White, 3.6% and 3) Blue, 1.8%. These results

suggested that consumers could discern between tenderness categories and were willing

to pay a premium for improved tenderness. Therefore, the factors that affect tenderness

need to be identified and studies need to be conducted to determine the best way to

ensure a tender product.









Factors Affecting the Tenderness of Beef

Differences in the rate and extent of postmortem tenderization are the principle

sources of variation in meat tenderness and are probably the source of inconsistency in

meat tenderness at the consumer level. To solve the tenderness problem, even greater

understanding of the mechanisms regulating meat tenderness and tenderization must be

gained (Koohmaraie et al., 1996). Tenderness is extremely difficult to measure

objectively because the chewing motions involved in mastication involve both vertical

and lateral movements of the human jaw as well as various in-between modifications,

which together produce the impression of tenderness (Pearson, 1963).

Before 1960, theories about meat tenderness tended to be dominated by the role of

connective tissue (Locker, 1985). Locker (1960) demonstrated the importance of the

myofibrillar component of tenderness and began the modern era of meat tenderness

research. Tenderization begins either at slaughter or shortly after slaughter, which results

from weakening of the myofibrils caused by proteolysis of proteins responsible for

maintaining structural integrity of the myofibrils (Wheeler and Koohmaraie, 1994).

Aging, a method for tenderization of meat by storage at above-freezing temperatures in

vacuum bags, is very important to assure a tender, acceptable product (Davey et al.,

1967). There are various theories about the reason for this phenomenon. Location within

muscles also has been shown to play a role in tenderness variations. There are tenderness

differences among muscles within the beef wholesale round, and these differences are

well documented (Ramsbottom et al., 1945; McKeith et al., 1985; Johnson et al., 1988;

Jones et al., 2001; Reuter et al., 2002). It has been established that a tenderness gradient

exists within steaks obtained for the longissimus muscle (Alsmeyer et al., 1965; Sharrah

et al., 1965; Smith et al., 1969). Another factor that may affect tenderness is quality









grade. Romans et al. (1965) found steaks containing moderate degrees of marbling to be

juicier than steaks possessing slight marbling although marbling level did not have a

significant effect on tenderness as determined by WBS. Walter et al. (1963) reported that

marbling did not exert any significant effect on tenderness, flavor orjuiciness scores.

Research reviews (Jeremiah et al., 1970; Parrish, 1974; Smith and Carpenter, 1974) have

emphasized low relationships between marbling and tenderness. Numerous investigation

of the relationship between marbling and beef palatability have shown that, although

there is a positive relationship between marbling degree and tenderness, this relationship

is weak at best (Parrish, 1974). Wheeler et al. (1994) reported that marbling explained

about 5% of the variation in palatability traits and that there was both tough and tender

meat within each marbling degree. So it is important to take into account these factors

when trying to determine the ideal way to create a predictability acceptable product to the

consumer.

Measurement of Tenderness

Because of savings in time and money and the difficulty of maintaining a well-

trained sensory panel, tenderness of cooked meat samples can be assessed much more

easily via WBS than trained sensory panel analysis (Shackelford et al., 1995). Harris and

Shorthose (1988) state that shear force does not accurately reflect tenderness differences

among muscles, however most investigators rely upon the WBS machine for objective

estimates of tenderness (Smith et al., 1978). Results of correlations between sensory

panel tenderness ratings and WBS values for the same muscles have suggested that WBS

is sufficiently reliable to use in lieu of taste panel results (Brady, 1937; Hay et al., 1953;

Kropf and Graf, 1959; Doty and Pierce, 1961; Pearson, 1963; Alsmeyer et al., 1966).









Shackelford et al. (1995) determined the relationship between WBS and overall

tenderness of 10 major beef muscles. Mean WBS differed little among muscles; however

muscles differed (P<0.05) greatly in overall tenderness ratings (psoas major (PM) =

infraspinatus (IF) > triceps brachii (TB) = longissimus dorsi (LD) = gluteus medius (GM)

= supraspinatus (SS) > biceps femoris (BF) = semimembranosus (SM) = quadriceps

femoris (QF)). These differences in overall tenderness among muscles were consistent

with previous findings ofRamsbottom and Stradine (1948), Shorthose and Harris (1990),

and Morgan et al. (1991). WBS was effective in detecting that PM and IF were more

tender than the others, but failed to detect and differentiate between the other muscles

studied. Differences in overall tenderness ratings among TB, LD, ST, GM, SS, BF, SM,

and QF could not be explained with any of the parameters of the WBS profile. The

relationship between peak load and overall tenderness within each muscle ranged from

very weak for GM (r2=0.00 to strong for LD r2=0.73) (Shackelford et al., 1995).

Some researchers have proposed relationships between WBS and consumer

perceptions of degree of tenderness. Shackelford et al. (1997a) classified a carcass as

"tender," "intermediate" or "tough" if its longissimus shear value at one or two days

postmortem was < 6 kg, 6 to 9 kg, or > 9 kg, respectively. A total of 100% of the

carcasses in the "tender" class had "low" WBS values at 14 days postmortem, 81% (exp

1) and 85% (exp 2) of the carcasses in the "intermediate" class had "low" WBS values at

14 days postmortem, and 74% (exp 1) and 67% (exp 2) of the carcasses in the "tough"

class did not have "low" WBS values at 14 days postmortem. In correlation studies,

WBS values were highly correlated with sensory tenderness (r = 0.78), which agrees with

the work ofWebb et al. (1964). Sensory tenderness, juiciness, and flavor were also









highly correlated with each other. Shackelford et al. (1991b) reported that 82% of

samples having WBS values less than 4.6 kg were rated "slightly tender" or higher, and

66% of samples having WBS values greater than 4.6 kg were rated less than "slightly

tender" by an in-home consumer panel. However, the relationship between tenderness of

the longissimus and tenderness of other muscles had been reported to be weak to

moderate (Slanger et al., 1985; Shackelford et al., 1995). Thus a minor muscle probably

could not be used as an indicator of longissimus tenderness. There would be limited

benefit to classifying the tenderness of other cuts based on tenderness of the longissimus

muscle (Shackelford et al., 1999).

There would likely not be much opportunity to classify round cuts according to

tenderness, on any basis, because Shackelford et al. (1997b) demonstrated that there is

little animal-to-animal variation in the tenderness of round cuts from youthful grain-fed

steers. Morgan et al. (1991) showed that WBS values indicate that a high percentage of

retail cuts from the chuck and round would receive overall tenderness rating scores less

than "slightly tender". Tenderloin and top blade steaks, which are consistently very

tender (Shackelford et al., 1995) could be guaranteed tender without product testing.

However, round cuts, which have a lot of random variation within each carcass

(Shackelford et al., 1997b), should not be guaranteed tender regardless of longissimus

tenderness (Shackelford et al., 1997a).

Beef palatability research studies often use traits such as marbling score, WBS, and

consumer or trained taste panel evaluations of tenderness, juiciness and flavor as

indicators of beef palatability (Platter et al., 2003). Platter et al. (2003) revealed

moderate to high correlations (P < 0.05) among mean marbling scores, WBS, and mean









consumer panel palatability ratings. The correlation between consumer tenderness

ratings and WBS was moderately high (r = 0.63). Marbling scores were correlations with

WBS, consumer tenderness ratings, consumer juiciness ratings, and consumer flavor

ratings were r = -0.31, -0.27, -0.34, -0.22, respectively. High, positive correlations (r =

0.80 to 0.84) were observed among all consumer sensory ratings (Platter et al., 2003). Of

the three sensory models developed by Platter et al. (2003), the most accurate was the

consumer tenderness rating at r2=0.56. The marbling and the WBS models were r2=0.053

and 0.225, respectively, for determining whether two-thirds of consumers would have

rated steaks as acceptable.

Slice force is another measurement of tenderness that has been studied. Wheeler et

al. (1999) established the longissimus dorsi to be tender if the day three WBS was < 5.0

kg when cooked to 700C. This value was equivalent to 23 kg of slice shear force that

Shackelford et al. (1999) used to test the efficacy of tenderness classification.

Trained sensory panel is also a measurement of tenderness in many studies. Smith

et al. (1978) demonstrated that the correlation for overall tenderness rating for 14 muscles

and shear force values was r = 0.48. These data suggested that shear force and sensory

panel tenderness ratings are sufficiently correlated to justify use of either measure for

assessing the tenderness of muscles in a beef carcass (Smith et al., 1978). However,

Lorenzen et al. (2003) reported a low correlation between trained sensory panels and

consumer sensory panels. There is an inherent difficulty in predicting consumer

responses from objective laboratory procedures, such as trained sensory panels and WBS.

There will continue to be important future uses for trained sensory panels, WBS

determination, and in home or other consumer evaluations of meat. How they can be









used to predict each other is a question that will be asked by meat science researchers for

years to come (Lorenzen et al., 2003).

Aging

Aging, a method for tenderizing of meat by storage at above-freezing temperatures

in vacuum bags, is very important to assure a tender, acceptable product (Davey et al.,

1967). Retailers and purveyors have relied on aging as a means of controlling beef

quality (Savell and Shackelford, 1992). Although aging is important in assuring tender

acceptable retail products, it creates problems in merchandising and in use of storage

facilities due to increased inventory of beef (Davey et al., 1967). This problem could be

alleviated by identification of the minimum period of aging necessary to assure the

desired level of tenderness (Smith et al., 1978).

There are two different methods of aging; wet and dry. Wet aging occurs in a

vacuum bag under refrigeration. In dry aging, the product is unpackaged and exposed to

air at a controlled temperature and relative humidity. Wet aging will produce acceptably

tender and flavorful products without loss of yield and the necessary amount of aging

space as with dry aging. For some processors, acceptable product palatability and

economic savings can be accomplished by using wet aging (Parrish et al., 1991). Parrish

et al. (1991) made a comparison between wet aging and dry aging and determined that

little or no cooler shrink was observed with wet-aged product. No measurable purge was

recorded for the wet-aged product either. Steaks for wet aging had higher scores (P <

0.01) for tenderness and overall palatability, although steaks from both wet and dry aging

provided very palatable products.

Postmortem storage of carcasses at refrigerated temperature has been known to

improve meat tenderness for many years and still remains an important procedure for









producing tender meat. Although improvement in meat tenderness is measurable both

subjectively and objectively, the exact mechanism of improvement in tenderness as a

result of postmortem storage still remains unclear. However there appears to be general

agreement that proteolysis of myofibrillar protein is the major contributor to meat

tenderization during postmortem storage (Dutson, 1983; Goll et al., 1983).

Mechanism of Aging

Tenderization begins either at slaughter or shortly after slaughter, which results

from weakening of the myofibrils caused by proteolysis of proteins responsible for

maintaining structural integrity of the myofibrils (Wheeler and Koohmaraie, 1994).

There are some animals that go through the tenderization process rapidly and could be

consumed after 1 day, whereas others could be consumed after 3, 7, or 14 days, and still

others would not be acceptable even after extended post-mortem storage (Wheeler and

Koohmaraie, 1994). The mechanism of postmortem aging is a very controversial issue

and many researchers have made an attempt to determine the specific mode of action.

Smith et al. (1978) demonstrated a characteristic improvement in beef tenderness during

postmortem aging in response to myofibrillar protein degradation by endogenous

proteases.

Koohmaraie (1995) suggested that calpain-mediated proteolysis of key myofibrillar

proteins is responsible for improvement in meat tenderness during post-mortem storage

of carcasses or cuts of meat at refrigerated temperatures. Differences in the potential

proteolytic activity of the calpain system result in differences in the rate and extent of

post-mortem tenderization. Koohmaraie (1995) has collected evidence indicating that,

within a species, 24 hr rather than at-death, calpastain activity is related to meat

tenderness. In beef, for example, calpastatin activity at 24 hr post-mortem is highly









related to beef tenderness after 14 days of postmortem storage. The estimates for the

relationship between calpastatin activity and meat tenderness vary, but up to 40% of the

variation in beef tenderness is explained by calpastatin activity at 1-day post-mortem

(Koohmaraie, 1995). Although endogenous enzyme systems are capable of softening or

degrading collagen (Dutson et al., 1980; Kopp and Valin, 1980-81; Wu et al., 1981),

those enzymes have not been shown to be released in sufficient quantities postmortem to

initiate such changes (Harris et al., 1992).

Calcium activated factor (CAF), also known as calcium-dependent protease (CDP),

is an endogenous structural protease active in postmortem beef muscle and is responsible

for myofibrillar protein degradation (disappearance of Troponin T and appearance of a

30,000 Dalton component) indicating postmortem aging (Olson et al., 1977). Of the

proteases located inside skeletal muscle, CDP and lysosomal enzymes appear to be the

best candidates for bringing about the tenderness changes during postmortem storage

(Dutson, 1983; Goll et al., 1983). CDP was initially identified in skeletal muscle by

Busch et al. (1972) and later purified by Dayton et al. (1976). Mellgren (1980) reported

the existence of a second form CDP. These two forms of the protease are now referred to

as CDP-I and CDP-II, according to the sequence of elution from a DEAE-cellulose

column at pH 7.5. CDP-I requires only very low concentration of calcium for 50%

activation, whereas CDP-II requires much higher calcium concentration (Goll et al.,

1983). CDP-I has also been labeled i-calpain, and CDP-II as m-calpain. Both of these

proteases are located primarily in the cytosol.

A second group of proteases that have been implicated in postmortem tenderization

are lysosomal enzymes. Of 13 reported lysosomal enzymes, only 7 have been shown to









exist in the lysosome of skeletal muscle cells (Goll et al., 1983). These enzymes have

acidic pH optima and, therefore, if involved in postmortem tenderization, they are most

involved once muscle approaches its ultimate pH. To explain a basis for meat

tenderization during postmortem storage, it has been postulated that one class of these

proteases or the synergistic action of both classes of proteases (CDP's and lysosomal

enzymes) is responsible for postmortem changes (Dutson, 1983; Goll et al., 1983;

Pearson et al., 1983). It is logical to assume that the class of proteases responsible for

postmortem aging should have higher activity in the carcasses with a high aging response

and vice versa (Koohmaraie et al., 1988). Illian et al. (2001) reported a third CDP, and

stated that the primary role of CDP-I and CDP-III was associated with meat tenderness in

vivo due to the high activity of these two enzymes.

Length of Aging

Another question that arises with the phenomenon of postmortem aging is how

long meat should be aged to reach optimum tenderness. Smith et al. (1978) stated that

aging of US Choice beef carcasses for 11 days will optimize tenderness, flavor, and

overall palatability of the majority of muscles in steaks and (or) roasts from the chuck,

rib, loin, and round when such cuts are ultimately broiled or roasted. Compared to shear

force at 5 days, aging for 8 days, 11 days, 21 days, and 28 days decreased shear force.

This was the case for sensory panel ratings also; aging for 11 days appeared to produce

optimal tenderization since further aging did not accomplish further reductions in shear

force (Smith et al., 1978). Doty and Pierce (1961) reported that aging of raw wholesale

cuts for two weeks substantially reduced shear force, but further aging did not result in

further shear force reductions.









Brooks et al. (2000) found that subprimal postfabrication times at the retail level

averaged 19 days. Overall, foodservice steaks were subjected to a postfabrication time of

32 days. Interestingly, top sirloins were aged an average of 32 days with a minimum of

20 days before fabrication in an effort to maximize tenderness. However, Harris et al.

(1992) reported that aging top sirloins up to 35 days postmortem had no effect on WBS

values. Lorenzen et al. (1998) reported that postmortem aging times of 14 days

maximized the tenderness of steaks from the chuck roll, rib, and shortloin. Reducing the

number of cuts that are not sufficiently aged before consumption may help increase

tenderness ratings and further reduce beef tenderness problems (Brooks et al., 2000).

Harris et al. (1992) found that top sirloin steaks did not respond to aging until 28 days

while top loin steaks demonstrated improvement in muscle fiber tenderness after only 7

days of postmortem aging and another increase after 28 days. Top sirloin steaks had

higher (P < 0.05) shear force values than did top loin steaks at each aging period. The top

sirloin steak demonstrated no decrease in WBS values in response to postmortem aging

(Harris et al., 1992). Connective tissue concentration also plays a major role in the aging

process. Connective tissue tended to remain relatively stable and intact during aging. If

the top sirloin steaks were less tender due to higher concentrations of connective tissue,

this lack of WBS decline would be expected (Harris et al., 1992). Overall in the study,

the top loin steaks showed a relatively steady decrease in shear force values as

postmortem aging time increased.

Miller et al. (1997) found that aging beef for 14 days improved the consistency of

beef tenderness and should be recommended as a processing control point for the beef

industry. This method would improve consumer acceptance of beef regardless of breed,









fatness, or processing variables. When steaks were aged for 7 days, WBS values of

Choice steaks tended to be more tender initially (6.6 kg) than Select steaks (6.1 kg).

However, aging for 14 days removed the grade effect (6.8 kg for Choice and 6.7 kg for

Select). The additional 7 days of aging raised the WBS of Choice steaks 0.26 kg but

raised the WBS of Select steaks twice as much (0.52 kg). Sustained tenderness scores

showed a similar pattern. If aged for 7 days, Choice steaks (6.5 kg) were scored higher

than Select steaks (6.0 kg). However, aging for 14 days removed the grade effect (6.7 kg

vs. 6.5 kg). Choice steaks aged for 7 days were scored the same as Select steaks aged for

14 days (6.5 kg) (Miller et al., 1997).

Rate of Muscle Aging

Tenderization of different muscles during aging in an individual carcass has been

shown to vary (Koohmaraie et al., 1988; Ouali and Talmant, 1990). For example, the rate

of tenderization of longissimus thoracis et lumborum (LT) was different for that of the

psoas major (PM) (Cridge et al., 1994). Rate of tenderization over the 14 day aging

period of LT was significantly (P < 0.05) higher than that of PM. These observations are

in accord with the results obtained by Koohmaraie et al. (1988) for the same two muscles

in the bovine (Ilian et al., 2001). Therefore, the rate of tenderization within various

muscles of the carcass needs to be considered when making recommendations about

aging. Koohmaraie et al. (1988) demonstrated that at 24 hour postmortem longissimus

(L), biceps femoris (BF), and psoas major (PM) muscles differed significantly in their

shear force values, but after 14 days of aging these differences were reduced

considerably. In terms of the aging response, L had the greatest response with a lesser

response in BF, and no response at all in PM at day 14. In this study the activities of

catheptic enzymes, B, H, L as well as the activities of CDP-I and II were examined in an









attempt to identify which protease class might be responsible for the observed differences

seen in aging response. Results indicated that regardless of the differences seen in aging

response, activities for cathespins (B, H, and B+L) were the same for all three muscles.

However, it may be possible that these enzymes could be differentially activated in vivo

by higher temperature and/or lower pH (Dutson, 1983) as seen in the PM muscle, thus

causing more aging response at the same enzyme concentration. In the case of CDP,

activities followed the same pattern as the aging responses; L which had the highest aging

response also had the higher CDP-I activity. In turn, PM, which displayed the least aging

response had the lowest CDP-I activity, and BF was intermediate in both CDP-I activity

and aging response. Based on the results of this and other experiments (Koohmaraie et

al., 1986, 1987) it was concluded that the initial levels of CDP-I activity determine the

aging response of a given muscle. The reason PM muscle had no aging response, even

though its CDP activity was about 50% of the L muscle, is not known. Koohmaraie

(1987) has demonstrated that about 50% of the aging response is completed by 24 hr

postmortem.

Sarcomere length may also be related to the aging response in that the muscles with

shorter sarcomere lengths had a greater aging response. At present no mechanism for a

relationship between sarcomere length and aging response can be proposed, however,

Dutson et al. (1976) demonstrated greater ultra structural alterations of z-lines when both

psoas major and stemomandibularis muscles were shortened. If CDP-I activity is

responsible for postmortem changes in the muscle, then its inactivation or unfavorable

conditions for its activation should prevent postmortem changes in the muscle. Also

activation of CDP-I or generation of favorable conditions for its activation should









accelerate the postmortem changes. This particular point in now being addressed by

attempting to manipulate animals and/or carcasses so that CDP-I would not be activated

and then examining postmortem changes in these carcasses (Koohmaraie et al., 1988).

Quality Grade

Marbling has often been implicated as a contributing factor to beef palatability and

is a major component in the USDA beef grading system (Jennings et al., 1978). Romans

et al. (1965) found steaks containing moderate degrees of marbling to be juicier than

steaks possessing slight marbling although marbling level did not have a significant effect

on tenderness as determined by the WBS. Also, Walter et al. (1963) reported that

marbling did not exert any significant effect on tenderness, flavor orjuiciness scores.

Research reviews (Jeremiah et al., 1970; Parrish, 1974; Smith and Carpenter, 1974) have

emphasized low relationships between marbling and tenderness.

Numerous investigations of the relationship between marbling and beef palatability

have shown that, although there is a positive relationship between marbling degree and

tenderness, this relationship is weak at best (Parrish, 1974). Wheeler et al. (1994)

reported that marbling explained about 5% of the variation in palatability traits and that

there was both tough and tender meat within each marbling degree. Data by Wheeler et

al. (1994) indicated a small, positive relationship of tenderness and juiciness with

marbling score, and a variation in tenderness may be decreased slightly as marbling

increases. The data also revealed a large amount of variation in sensory tenderness rating

and shear force within one marbling score or another.

Various studies (Blumer, 1963; Pearson, 1966; Parrish, 1974; Jeremiah, 1978) have

revealed that between 5 and 10% of the variation in tenderness can be accounted for by

marbling degree. According to Smith et al. (1984), due to the USDA quality grading









standards for carcass beef and their implied segregation of meat based on palatability, the

US beef industry has placed a high value on marbling at the 12th rib interface of the

longissimus thoracis. The emphasis on marbling in determining carcass value is based on

the slight increases in juiciness, flavor, and tenderness that are obtained as marbling is

increased. There are, however, several problems with palatability estimation based solely

on marbling score. An abundance of research expanding over the last 30 years has

indicated that marbling/intramuscular fat has a low relationship to palatability. The

variation in marbling in the longissimus thoracis has little effect on palatability of other

muscles (Smith et al., 1984). The pursuit of higher amounts of marbling, however,

results in more time on feed and, thus, in fatter, lower-yielding carcasses. Use of a visual

assessment of the amount of fat exposed in a cross-section of the longissimus thoracis at

the 12th rib as the primary determinant of the value of the entire carcass may not be

justified (Wheeler et al., 1994).

Association of Level of Marbling and Quality Grade to Tenderness

Many researchers have reported that tenderness, juiciness, and flavor increase with

increasing degrees of marbling in a direct, linear relationship (McBee and Wiles, 1967;

Jennings et al., 1978; Dolezal et al., 1982), whereas others have reported very low or

nonexistent associations (Carpenter et al., 1972; Parrish et al., 1973; Parrish 1974,

Dikeman and Crouse, 1975; Davis et al., 1979; Smith et al., 1984; Brooks et al., 2000).

Mean WBS differences seem to be small between chuck cuts from different quality

grades. However, the frequency distribution of shear force values indicates

approximately 10% more cuts from Select (24 of 58) and No-roll (36 of 87) grades

having 4.0 kg of force or greater, compared with Choice chuck cuts (70 of 220) (Morgan

et al., 1991). No noticeable differences in WBS or variation in tenderness were observed









between round cuts differing in quality grade (Morgan et al., 1991). Smith et al. (1984)

stated that marbling is of very limited value in explaining differences in sensory panel

ratings of round steaks compared to loin and rib steaks. Morgan et al. (1991) determined

that USDA quality grade failed to control the variation in panel ratings or WBS values to

the degree necessary to ensure consistent beef products to the consumer.

Regardless of the amount of external fat, loin steaks possessing modest or above

marbling, had lower WBS values and higher tenderness and juiciness ratings (P<0.05)

than steaks containing slight or lower marbling (Jennings et al., 1978). Wheeler et al.,

(1994) reported that although mean palatability scores were in the acceptable range,

regression of WBS and sensory traits on marbling indicates the low association of

marbling score to meat palatability, despite the fact that palatability traits generally

increase as marbling level increases. Carcass characteristics and measurements are low

in their relationships to tenderness attributes with marbling scores having the highest

correlations. Based on these results obtained from Jennings et al. (1978) it would appear

that the influence of marbling on palatability varies depending on degree of marbling.

George et al. (1997) reported that Choice rib steaks have lower (P < 0.01) WBS

values at day 14 and day 28 than rib steaks from Select carcasses. Similarly, rib steaks

for Choice carcasses had higher ratings (P < 0.01) for muscle fiber tenderness and overall

tenderness. Quality grades in the present study were useful for segregating carcasses

according to their likelihood of yielding steaks differing in palatability and should

continue to be useful until a system is identified to augment or assist the current use of

differences in maturity and marbling for such purpose (George et al., 1997).









The "Insurance Theory"

The "insurance theory" or the ability of marbling to maintain tender meat when

cooked to high end point temperatures has been supported by some studies (Luchak et al.,

1990), but not others (Parrish et al., 1973). Smith and Carpenter (1974) suggested that

the "insurance theory" means that, by having higher degrees of marbling, the use of high-

temperature, dry-heat methods of cookery and/or the attainment of advanced degrees of

final doneness will not adversely affect the ultimate palatability of the cooked meat.

Marbling would provide some insurance that the meat cooked too rapidly, too

extensively, or by the wrong method of cookery would still be palatable. Fatty tissue

does not conduct heat as rapidly as lean tissue, so it is possible that marbled meat can

endure higher external cooking temperatures without becoming overcooked internally.

This theory suggests that dry-heat cookery is suitable only for naturally tender cuts of

beef such as the rib and loin from Prime, Choice, and Select carcasses and the top round,

rump, and blade chuck from Prime and Choice carcasses (Smith and Carpenter, 1974).

Luchak et al. (1990) reported that Select top loin steaks were tougher at higher

temperatures than Choice top loin steaks. Choice steaks were also juicier, higher in fat,

cooked slower, and were more tender when compared with Select steaks (Luchak et al.,

1990). Parrish et al. (1991) found that Prime and Choice steaks scored more tender (P <

0.01) than Select steaks when cooked to an internal temperature of 630C. These results

agreed with those reported by Smith et al. (1984), but disagreed with Goll et al. (1965)

and Parrish et al. (1973) who found no statistically significant effect of quality grade on

palatability of steaks when cooked to an internal temperature of 540C.

Parrish et al. (1973) reported that internal cooking temperature of rib steaks is a

much more important factor in palatability than marbling, and that degree of marbling,









and its interaction with internal cooking temperature, had essentially no effect on

palatability characteristics. Parrish et al. (1991) found that although certain palatability

attributes were statistically different between quality grades and cuts, all were considered

palatable. WBS values were significantly influenced by USDA quality grade. Steaks

that graded Choice had lower WBS values than Prime or Select steaks. Choice loin

steaks also received higher sensory scores for tenderness, juiciness, and overall

palatability than Select loin steaks. Prime grade loin steaks and roasts scored higher on

the trained and untrained sensory panels by being more tender, juicy, and having a more

intense desirable flavor. This disagreed with published data in which consumer panelists

found no difference in sensory characteristics between quality grades (Francis et al.,

1977; Nauman et al., 1961).

Differences Detected by Consumers

Neely et al. (1998) evaluated three kinds of beef steaks from four USDA quality

grade levels in four major cities on consumer satisfaction of moderate to heavy beef

users. Top Choice steaks were rated higher (P < 0.05) in overall like than the remainder

of the grades (Low Choice, High Select, and Low Select). Ratings for High Select top

loin steaks did not differ (P > 0.05) for those for Low Choice or Low Select steaks;

however, overall like ratings for Low Choice differed for ratings for Low Select. Grade

had no effect (P > 0.05) on overall like among the top sirloin steaks. Top Choice top

round steaks were rated higher (P < 0.05) than the other grades of top round steaks for

overall like. Across all USDA quality grades, ratings for Overall like for top loin steaks

were higher (P < 0.05) than those for top sirloin steaks, and ratings for top sirloin steaks

were higher (P < 0.05) than those for top round steaks. For overall like ratings, effect of









USDA quality grade was cut-specific. The cut most affected was the top loin steaks

which agree with the findings of Smith et al. (1987).

The USDA quality grade has been a controversial topic for many decades. Some

believe strongly that grades perform well in sorting and categorizing beef for the

marketplace. Others believe that the relationship between marbling and palatability is too

low to serve as any real basis for identification of products for consumers. Findings from

Neely et al. (1998) and Smith et al. (1987) suggested that USDA quality grade may be

limited in the sorting of products for the marketplace derived from the longissimus

muscles, and that it has less effect on the remaining major muscle of the beef carcass.

Walter et al. (1965), utilized 72 carcasses that represented maturity groups A, B and

E and marbling groups moderately abundant, slightly abundant, modest, small, traces,

and practically devoid, as determined by USDA Official Standards for Grades of Beef

Carcasses. Analysis of variance and correlation coefficients demonstrated that marbling

had no effect on tenderness but that tenderness decreased with advancing carcass

maturity. Nearly 85% of the variation in ether extract could be accounted for by

marbling (r = 0.92), indicating that the subjective scoring of marbling was in close

agreement with objective determinations (Walter et al., 1965). As demonstrated in

numerous studies, marbling did not significantly affect tenderness (Alsmeyer et al., 1959;

Blumer, 1963; Cover and Hostetler, 1960; Cover et al., 1956, 1958; Palmer et al., 1958;

Tuma et al., 1962, 1963; Wellington and Stouffer, 1959). Using the same data, analysis

of variance had no effect on sensory scores for tenderness, juiciness, or flavor (Goll et al.,

1965).









Location

There are tenderness differences among muscles within the beef wholesale round,

and these differences are well documented (Ramsbottom et al., 1945; McKeith et al.,

1985; Johnson et al., 1988; Jones et al., 2001; Reuter et al., 2002). Ginger and Weir,

(1958) and Christians et al. (1961) have also conducted research to show that there is

indeed definable intramuscular tenderness variation within certain beef round muscles. It

has also been established that a tenderness gradient exists within steaks obtained from the

longissimus muscle (Alsmeyer et al., 1965; Sharrah et al., 1965; Smith et al., 1969). The

cores from the medial and dorsal portion of the longissimus dorsi muscle were more

tender than those from the more lateral positions. Henrickson and Mjoseth (1964) found

that longissimus dorsi steaks from the ninth thoracic vertebra were significantly (P <

0.01) more tender than those from the 11th thoracic vertebra when measured with WBS.

Neither maturity, marbling or core location had a significant effect on tenderness as

determined by WBS by these researchers.

Such variations demonstrate that meat is not a homogenous material (Walter et al.,

1965). However, researchers are not in complete agreement about this gradient. Cover et

al. (1962) found that there were not any differences in cores from the longissimus dorsi.

Romans et al., (1965) also found no significant core location differences in WBS

tenderness. When evaluated by the taste panel, steaks adjacent to the ninth thoracic

vertebra were slightly more tender than those adjacent to the 11th thoracic vertebra, but

these differences in taste panel tenderness were nonsignificant, however Henrickson and

Mjoseth (1964) found that the longissimus dorsi steaks from the ninth thoracic vertebra

were significantly (P<0.01) more tender than those from the 11t thoracic vertebra when

measured with WB S.









Shackelford et al., (1997b) tested the effects of location and aging. Biceps femoris

(BF) and semitendinosus (ST) were obtained from A maturity, grain-fed, crossbred steers

(n=25) at 16 d postmortem. Steaks were removed from each muscle for determination of

shear force and tenderness rating at each of three locations (A=proximal end, B=center,

C=distal end). They were removed from the right round of each carcass and trimmed of

all subcutaneous and intermuscular fat, vacuum packaged, and held at 20C. Cuts were

aged to 16 d postmortem because the National Beef Tenderness Survey (Morgan et al.,

1991) indicated that the average aging time for beef round cut at US retail stores was 16

days. In agreement with Shackelford et al. (1995) comparison of multiple beef muscles

revealed that tenderness rating was higher for BF than for ST (P < 0.01). Sensory

tenderness ratings were more repeatable than shear force for BF (R = 0.5 vs. 0.3) and ST

(R = 0.6 vs. 0.56). However, all of the estimates of repeatability were much less than

values that Wheeler et al. (1997) obtained for beef longissimus using similar laboratory

procedures (R= 0.79 vs. 0.9). Location did not affect (P > 0.05) BF WBS; however BF

tenderness ratings were higher (P < 0.05) for location A than for locations B and C.

WBS decreased (P < 0.05) from the proximal end to the distal end of the ST. Also, ST

tenderness ratings were lower for location A than locations B and C. The proximal end

of the ST contained heavy bands of connective tissue, which might explain the reduced

tenderness rating of that location. However, the increased WBS of the proximal end of

ST cannot be assigned to the presence of heavy bands of connective tissue because those

bands of connective tissue were avoided when removing cores for shear force. Because

of the large effect of location on ST tenderness, there might be merit to target different

portions of the ST for specific uses. For example, the more tender portion (distal half) of









the ST might be suitable for use as broiled/grilled steaks, whereas the tougher portion of

the ST might be more suitable for use as roasts or cubed steaks (Shackelford et al.,

1997b).

In a similar study by McBee and Wiles (1967), steaks cut at the third lumbar

vertebra were tested for differences in WBS values among dorsal, medial and lateral

locations within steaks from the longissimus dorsi. The dorsal portion had a significantly

lower mean WBS value than the other two locations. There was no significant difference

in WBS values between the medial and lateral locations, although the medial location had

the highest mean WBS value. These results agree with those of Alsmeyer et al. (1965)

and Tuma et al. (1962).

A number of researchers have investigated potential tenderness gradients across the

longissimus dorsi muscle (Hostetler and Ritchey, 1964; Alsmeyer et al., 1965; Crouse et

al., 1989). Kerth et al. (2002) found that core location had a significant effect (P < 0.01)

on WBS in both 7 and 14 days of postmortem aging. In both aging periods there were

regions of WBS values that differed (P < 0.05) across the cross section of the longissimus

dorsi producing a tenderness gradient. In general there was a lateral to medial WBS

gradient across the longissimus dorsi steaks (P < 0.05). While a dorsal to ventral gradient

was evident in both aging periods, the lateral to medial gradient was the most

predominant. Cores from the center of steaks tended to have the most predictive capacity

of average WBS (Kerth et al., 2002).

Location effects add difficulty in merchandising steaks from new cuts taken from

the chuck and the round. The retail sector must be innovative in merchandizing

techniques to maintain steak thickness and minimize portion size (Savell and









Shackelford, 1992) while taking into account the possible variations in tenderness due to

location effects.

The objective of this study was to determine the aging patterns of nine selected

muscles from the chuck and the round for two quality grades of beef: USDA Select and

the upper 2/3 of USDA Choice. The effects of quality grade, aging, and location on

tenderness were determined. Tenderness was determined by Warner-Bratzler shear force

from these nine muscles of locomotion from the two different quality grades. The

muscles were also divided into quadrants to test location effects.














CHAPTER 3
THE EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON WBS FORCE
VALUES ON SELECTED MUSCLES OF LOCOMOTION OF THE BEEF CHUCK
AND ROUND

Introduction

Recently, University of Florida and University of Nebraska Scientists characterized

thirty-seven muscles of the beef chuck and round relative to size, shape, palatability, and

composition (National Cattlemen's Beef Association (NCBA), 2000). This study

revealed that a significant number of these muscles, when removed separately and cut

across the grain, were very acceptable in sensory panel scores. The researchers

concluded that there are numerous muscles that could be up-graded in value by cutting

them into steaks rather than selling them as part of a roast or grinding into ground beef

(NCBA, 2000). Kukowski et al. (2004) found the complexus, serratus ventralis, triceps

brachii, and the infraspinatus were acceptable to consumers as steaks. By using these

muscles as steaks instead of roasts, more total dollars could be generated for beef and

could lead to greater profits (Kukowski et al, 2004). As the industry begins to isolate

individual muscles of the chuck and round for merchandising as steak cuts, more

knowledge about how these muscles respond to postmortem aging is required in order to

assure tenderness.

In recent years, economic pressures have challenged the livestock and meat

industries to seek ways of producing meat products that will enable consumers to receive

maximum palatability benefits at the lowest costs (Morgan et. al., 1991). The increased

demand for middle cuts, combined with the decreased demand for end meats, has resulted









in the average retail beef process remaining relatively unchanged during the 1990s

(Kukowski et al., 2004). Due to consumer demand for smaller portion sizes, beef

retailers have been forced to fabricate steaks from cuts of meat (round and chuck

subprimals) that previously were merchandised solely as roasts (Shackelford et al., 1995).

With traditional roasts cuts being marketed as individual muscle steaks instead of roasts,

valued could be added to the beef carcass (Kukowski et al., 2004). The round represents

approximately 22% of the weight of a typical beef carcass and contains some of the least

tender muscles of the carcass (Ramsbottom et al., 1945; Jones et al., 2001). Rhee et al.

(2004) found that the adductor, semimembranosus, gluteus medius, and semitendinosus

all from the round; and the supraspinatus from the chuck had high WBS force values

(WBS = 4.29 kg). Savell and Smith (2000) reported that the chuck represents about 30%

of the total carcass weight. That is approximately 52% of the carcass that is currently

used primarily as ground beef and roasts.

Miller et al. (2001) found that consumers were willing to pay a premium for

steaks that reach certain levels of tenderness. One of the most prevalent and non-invasive

methods of postmortem tenderization is "aging" meat at refrigerated temperatures

(Parrish, 1997). Much of the published work to date has focused on the longissimus

muscle (Jennings et al. 1978, Shackelford et al. 1991a, and Parrish, 1997). As the

industry begins to isolate individual muscles of the chuck and round for merchandising as

steak cuts that will be cooked commonly with a dry cooking method, then more

knowledge about how these muscles respond to postmortem aging is required. Parrish

(1997) stated that tenderloin and eye of round have a different aging pattern from the

longissimus muscle, but other beef muscles were not mentioned in that review. Parrish et









al. (1991) also found that beef longissimus from USDA Choice aged similarly to USDA

Select longissimus, but other muscles were not studied.

The economic incentives for the industry to improve the tenderness of beef must

be established before significant improvements in the consistency and palatability of beef

will occur (Miller et al., 1998). Kukowski et al. (2004) asked panelist to assign a

price/0.45 kg (0=would not buy, 10=$10/0.45 kg). Consumers were willing to pay

$5.68/0.45 kg for the infraspinatus, and $5.15/0.45 kg for the triceps brachii. This could

provide a good incentive for retailers to use these individual muscles as steak cuts. Other

cuts from the Kukowski et al. (2004) study that were found to be acceptable as steaks

cuts were the serratus ventralis ($4.78/0.45 kg), and the complexus ($4.75/0.45 kg).

According to Miller et al. (1998), the most important factor in a tenderness study with

consumers was to establish that a range in beef tenderness from tender to tough exists.

The range given in this study was greater than 2.0 and less than 7.0 kg of shear force.

Research has shown that consumers can detect changes in tenderness similar to those

found with instrumental measurements such as WBS force (Miller et al., 1995;

Shackelford et al., 1991b; Boleman et al., 1997). Therefore, WBS values can be used as

an indicator of the value relationship for tenderness.

Some possible factors that affect tenderness have been identified as postmortem

storage time and temperature (aging) (Smith et al., 1978; Eilers et al., 1996; Mitchell et

al., 1991), the quality grade of the carcass (Goll et al, 1965; McBee and Wiles, 1967,

Smith and Carpenter, 1974), and a possible location effect within individual muscles

(Kerth et al., 2002; Reuter et al., 2002; Rhee et al., 2004). Continued work is needed on

improving meat tenderness, primarily for retail cuts from the round and chuck. If









consumers are willing to pay more for guaranteed tender beef products (Boleman et al.,

1997), additional work needs to be conducted to investigate aging patterns of other

muscles of the chuck and round so that the highest and best use for each muscle can be

determined. If certain muscles do not respond to aging then it seems a waste of resources

to do so, and other methods of ensuring tenderness need to be explored. If muscles from

the chuck and round do respond to aging, then targeting or customizing aging time to

individual muscles and desired level of tenderness would seem appropriate.

Materials and Methods

Institutional Meat Purchase Specifications (IMPS) (North American Meat

Processors, 1988) 115 2-piece boneless chucks and IMPS 167A peeled knuckles were

purchased from a major packer of known USDA grade and slaughter date. Two grades of

cuts were studied: USDA Select and the upper 2/3 of the USDA Choice grade. Eight

subprimals of each grade were immediately shipped to the University of Florida Meats

Laboratory for muscle separation. The IMPS 115 2-piece chuck was separated and the

following muscles were selected for study: infraspinatus, triceps brachii lateral head,

triceps brachii long head, serratus ventralis, complexus, splenius, and rhomboideus.

The IMPS 167A knuckle was also separated and the vastus lateralis and rectus femoris

were evaluated. These nine muscles were selected because of the possibility that these

could be used as steak cuts where tenderness is critical due to the probability that they

would be cooked with a dry cooking method, based on results from the Muscle Profiling

Study conducted by University of Florida and University of Nebraska in conjunction with

National Cattleman's Beef Association (NCBA, 2000).

Each muscle was divided into four portions, progressing from anterior to posterior

orientation to the carcass, or from dorsal to ventral orientation to the carcass depending









on muscle fiber orientation: A was the 1st 25% portion of the muscle, B was the 2nd 25%

portion of the muscle, C was the 3rd 25% portion of the muscle, and D was the 4th 25%

portion of the muscle. One steak was removed for evaluation from each portion of the

muscle to be studied. For small muscles the entire portion may have been used as the

steak. Postmortem aging was conducted for 7, 14, 21, or 28 days at 2 + 20C. Individual

steaks were vacuum sealed in Cryovac B550T (Sealed Air Corp., Duncan, SC) bags and

subsequently heat shrunk in 820C water as per manufacturers recommendation. A Latin

square was used to assign each steak into one of four postmortem aging treatments.

There were eight 2 piece chucks from the USDA Select grade numbered one through

eight, and eight knuckles from the USDA Select grade numbered one though eight. The

same numbering system was used for the subprimals from the USDA Choice grade. For

pieces one through four, the postmortem aging period was rotated clockwise for each

location. For pieces five through eight, the positions for postmortem aging period was

rotated counter-clockwise. This was done to remove muscle location effect on WBS

values. Also, this treatment allocation method allowed for location effect to be tested and

determined statistically.

After achieving the appropriate postmortem aging treatment, steaks were frozen at -

400 C then transferred to a -200 C holding freezer until WBS could be conducted. Eight

of each of the subprimals for each grade were sampled and replicated twice for a total of

32 subprimals boned to generate 288 muscles. Four steaks per muscle produced 1152

observations for this trial.

Steaks were thawed for 18 hours at 2 to 40 C then broiled on Farberware

(Farberware, Bronx, NY) open-hearth broilers to an internal temperature of 71C









(American Meat Science Association, 1995). The housing and drip pans of each broiler

were covered with aluminum foil and preheated for 15 min. Copper-constantan

thermocouples attached to a potentiometer were placed in the approximate geometric

center of each steak and used to record internal temperature. Steaks were turned when

the internal temperature of 350 C was reached and removed from the broiler when the

internal temperature reached 710C. Samples were allowed to cool at 2 to 40 C for

approximately 18 hours and then 4 to 6 1.27-cm cores were removed from each steak,

parallel to fiber orientation, for shear force determination. Shear force determinations

were conducted on an Instron (Canton, MA) universal testing machine equipped with a

WBS head, with a crosshead speed of 200 mm/min.

Least squares, fixed model procedures of SAS (2001) were used to analyze these

data. This study was analyzed as a split-plot design where quality grade and muscle was

the main-plot and postmortem aging and location were the sub-plots which were assigned

using a Latin square design.

Results and Discussion

Mean values and other descriptive statistics are presented in Table 3-1 for the nine

muscles evaluated in this study. The results of the current study agree with that of Rhee

et al. (2004). For the muscles that were evaluated in both studies, the infraspinatus the

most tender muscle, followed by the rectus femoris. Rhee et al. (2004) showed a higher

WBS for the triceps brachii than the rectus femoris, where as in the current study, the

triceps brachii-lateral head and the triceps brachii-long head were equivalent in WBS to

the rectus femoris. For consumer panel ratings, Kukowski et al. (2004) also found the

infraspinatus to be the most tender muscle followed by the triceps brachii, the serratus









ventralis, and the complexus, which are comparable to the WBS results obtained in the

current study.

Table 3-2 gives the mean and standard deviation for the nine muscles used in this

study. The rhomboideus, vastus lateralis, and splenius muscles were the least tender tier

of the muscle groups and the infraspinatus muscle was by far the most tender of the nine

muscles. The intermediate group of muscles that were very similar in WBS included the

triceps-lateral and long head, complexus, serratus ventralis, and rectus femoris. Variation

in shear values appeared to be directly related to average shear value. For instance, the

rhomboideus had the highest standard deviation and the highest average WBS value. In

comparison, the infraspinatus had the lowest standard deviation and average shear value.

The analysis of variance revealed a significant grade by postmortem aging

interaction effect; Table 3-3 gives interaction mean values for these two factors. The

USDA Select Grade steaks had a significant reduction in shear force values between 7

and 14 days of about 10 percent. There was no significant reduction of shear values after

14 days. Doty and Pierce (1961) reported that beef from all carcass grades had

substantially reduced shear force requirements after two weeks of aging, but further aging

did not reduce shear force values. For steaks from the upper two-thirds of the Choice

grade, no significant improvement in WBS values was noted after 7 days postmortem

aging. This is similar to results from Smith et al. (1978) which reported that aging

beyond 11 days did not accomplish further reductions in shear force requirements, and

Mitchell et al. (1991) reported little advantage in extending aging beyond 10 days. The

effect of grade was only significant at day 7 and day 21 of postmortem aging (Table 3).

If an end-user has the ability or can afford to hold steaks for 28 days postmortem, then









according to these data, USDA Select would be equivalent to the upper two-thirds of the

Choice grade for WBS force values.

There was a significant main effect for USDA Grade and for postmortem aging;

these values are also presented in Table 3-3. When averaged across all postmortem aging

periods, grade only influenced WBS values by about 5 percent. The grade effect was

greatest at 7 days postmortem and lessened as postmortem aging increased. If grade is

ignored and only postmortem aging considered, it appeared that there was a significant

decrease in WBS values between 7 and 14 days aging and 21 and 28 days aging. These

data would suggest that 14 days aging would be an appropriate recommendation if end

users could not hold product an entire 28 days aging period. This 14 day aging

recommendation agrees with that of other researchers (Doty and Pierce, 1961; Eilers et

al., 1996; Miller et al., 1997). Miller et al. (1997) suggested that aging beef for 14 days

would improve the consistency of beef tenderness and should be recommended as a

processing control point for the beef industry to improve consumer acceptance of beef

regardless of breed, fatness, or processing variables.

Table 3-4 presents the effect of muscle location on WBS force values by muscle.

Only four of the nine muscles were significantly impacted by anatomical location on

shear force values, those included the complexus, rhomboideus, vastus lateralis, and

rectus femoris. Both the complexus and rhomboideus muscles had higher shear force

values going from the anterior to the posterior portion of the muscle. Both of these

muscles run along the top of the shoulder and neck in close proximity. For the

complexus, the anterior 25-percentile muscle portion had higher shear value than the

center 50 percent of the muscle. The quartile closest to the wholesale rib was the lowest









in shear value and about 26 percent lower in shear value than the quartile found closest to

the head. Similar results were noted for the rhomboideus, except not as extreme as noted

for the complexus. The anterior one-half of the muscle was approximately nine percent

higher in shear value than the posterior quartile of the muscle.

The two muscles evaluated from the knuckle were opposite in location effect when

compared to the two previously mentioned muscles. Both the vastus lateralis and rectus

femoris had increasing shear value when going from the anterior to posterior portion of

the muscle. The anterior one-half of the vastus lateralis was approximately 10 percent

more tender than the posterior quadrant of the muscle from the chuck. The rectus femoris

was similar in its aging pattern to the vastus lateralis muscle in that the anterior 25

percent was more tender than the posterior 25 percent of the muscle. The middle 50

percent of the muscle was intermediate in shear values to the two end quadrants and not

statistically different. Reuter et al. (2002) found a tenderness variation within the biceps

femoris and the semimembranosus, but not within the adductor and the semitendinosus.

For the biceps femoris and the semimembranosus the lowest shear force values were at

the anterior end, highest shear force values at the posterior end and intermediate shear

values in the middle (Reuter et al. 2002), which is similar to the rectus femoris in the

current study. These data would suggest that for at least some individual muscles of the

chuck and round, location should be considered when fabricating and merchandizing

these muscles. For other muscles, location within the muscle need not be considered

when merchandizing decisions are made.

Postmortem aging affects by muscle interaction was tested within subprimals and

found to be not significant (P = 0.53). This suggests that postmortem aging affects all









muscles in a similar manner for WBS force values. Therefore, aging recommendations

for the nine muscles studied in this project can be identical but USDA grade or

intramuscular fat content would need to be considered. In contrast, Parrish et al. (1991)

reported that there was no difference between the aging rates of USDA Choice versus

USDA Select longissimus, but aging rates were significantly influenced by USDA quality

grade. Steaks that graded Choice had lower WBS values than Prime or Select steaks

(Parrish et al. 1991). It is important to note that there was a greater difference in grade or

intramuscular fat in the present study because the Select grade was compared to the upper

two-thirds of the Choice grade. Parrish (1997) noted that tenderloin and eye of round had

different aging patterns from the longissimus muscle whereas muscles in the present

study appeared to age in a similar fashion. It is important to note also that in the Parrish

study, muscles of locomotion were compared to muscles of support where in the present

study all muscles would be considered locomotive muscles. Miller et al. (1997) reported

that sensory scores for USDA Choice steaks were higher than USDA Select, but USDA

quality grade did not affect WBS. Kukowski et al. (2004) also reported USDA Choice

steaks to have higher sensory panel scores than USDA Select steaks, but did not test

WBS.

Implications

Postmortem aging affects all of the muscles evaluated in this study in a similar

fashion. Therefore, consistent recommendations about postmortem aging can be given

for these muscles. This study revealed that USDA grade would have an effect on

postmortem aging, in that for muscles from the upper two-thirds of USDA Choice grade

was not significantly improved after seven days postmortem aging. Muscles from the









USDA Select grade should be aged a minimum of 14 days postmortem to achieve

optimum tenderness.

Location within a muscle was found to have an effect on WBS values in four of the

nine muscles evaluated. This would indicate that muscles would have to be treated on an

individual basis when fabrication and merchandising individual retail cuts or portions

from muscles of the chuck and round. For some muscles, location within the cut can be

ignored and for others location must be considered for tenderness enhancement or

product utilization.












Table 3-1. Means, standard deviations, minimum, and maximum values for WBS at 14 days postmortem aging by muscle
Subprimal Muscle Mean, kg SD Minimum, kg Maximum, kg
Chuck Triceps-lateral 3.8 0.66 2.1 5.2
Triceps-long 3.8 0.67 2.5 5.3
Splenius 4.5 0.97 3.0 6.4
Complexus 3.7 0.97 2.3 7.2
Rhomboideus 5.2 1.13 3.3 7.3
Serratus ventralis 3.7 0.78 2.1 5.2
Infraspinatus 2.8 0.58 1.8 4.5
Knuckle Vastus lateralis 4.5 0.96 3.1 7.2
Rectus femoris 3.8 0.78 2.4 5.5
Each muscles mean represents an average of 768 measurements.












Table 3-2. WBS values for muscles of the chuck and knuckle averaged across all aging periods
Subprimal Muscle Mean, kg SD
Chuck Triceps lateral head 3.9d 0.79
Triceps long head 3.8de 0.76
Splenius 4.4C 1.07
Complexus 3.6e 0.85
Rhomboideus 5.0a 1.27
Serratus ventralis 3.6e 0.84
Infraspinatus 2.8f 0.75
Knuckle Vastus lateralis 4.7b 0.97
Rectus femoris 3.8de 0.97
abcdet Means with the same superscript in the same column are not significantly different at P<0.05 according to LSD=0.225. Each
muscles mean represents an average of 768 measurements.












Table 3-3. WBS values by grade and aging treatment
Postmortem aging (days)


Grade 7 14 21 28 Average
Mean, kg SD Mean, kg SD Mean, kg SD Mean, kg SD Mean, kg SD
Select 4.4ax 1.32 4.0bx 1.01 4.1bx 1.15 3.9bx 0.91 4.1x 1.12

Top Choice 3.9ay 1.23 3.9ax 1.09 3.8ay 1.05 3.8ax 1.11 3.9y 1.12

Average 4.2a 1.30 4.0b 1.05 4.0bc 1.11 3.8c 1.01 4.0
bc Means with same superscript on same row are not significantly different at P<0.05 according to LSD=0.21 for the individual
grades, and LSD=0.15 for the average of the grades. y Means with same superscript on same column are not significantly different at
P<0.05 according to LSD=0.22 for the individual age groups, and LSD=0.18 for the average of all age groups. Each grade mean
represents an average of 432 measurements.












Table 3-4. WBS values by location


Location
A


C


D


B


Subprimal Mean, kg SD Mean, kg SD Mean, kg SD Mean, kg SD

Chuck Triceps-lateral 3.7a 0.72 3.9a 0.88 4.0a 0.74 4.1a 0.79
Triceps-long 3.8a 0.86 3.8a 0.78 3.8a 0.66 4.0a 0.74
Splenius 4.3a 1.00 4.5a 1.07 4.3a 0.86 4.7a 1.29
Complexus 4.2a 1.02 3.7b 0.75 3.7b 0.74 3.1c 0.51
Rhomboideus 5.3a 1.20 5.2a 1.37 5.1ab 1.28 4.8b 1.21
Serratus ventralis 3.6a 0.70 3.6a 0.96 3.5a 0.64 3.7a 1.05
Infraspinatus 2.9a 0.75 2.8a 0.73 2.7a 0.82 2.7a 0.68
Knuckle Vastus lateralis 4.5b 0.85 4.5b 0.89 4.8ab 1.1 5.0a 1.04
Rectus femoris 3.4C 0.83 3.8bc 0.88 3.9b 1.12 4.1a 0.92

abc Means with same superscript in same row are not significantly different at P<0.05 according to LSD=0.45. Each muscle mean is an
average of 1,728 measurements.














CHAPTER 4
EFFECTS OF QUALITY GRADE, AGING, AND LOCATION ON COOK AND
THAW LOSS OF SELECTED MUSCLES OF LOCOMOTION OF THE BEEF
CHUCK AND ROUND

Introduction

Recently, University of Florida and University of Nebraska Scientists characterized

thirty-seven muscles of the beef chuck and round relative to size, shape, palatability, and

composition (NCBA, 2000). This study revealed that a significant number of these

muscles, when removed separately and cut across the grain, were very acceptable in

sensory panel scores. Their conclusions were that there are numerous muscles that could

be up-graded in value by cutting them into steaks rather than selling them as part of a

roast or grinding into ground beef (NCBA, 2000). Kukowski et al. (2004) found the

complexus, serratus ventralis, triceps brachii, and the infraspinatus were acceptable to

consumers as steaks.

In recent years, economic pressures have challenged the livestock and meat

industries to seek ways of producing meat products that will enable consumers to receive

maximum palatability benefits at the lowest costs (Morgan et. al., 1991). With traditional

roasts cuts being marketed as individual muscle steaks instead of roasts, valued could be

added to the beef carcass (Kukowski et al., 2004). The round represents approximately

22% of the weight of a typical beef carcass and contains some of the least tender muscles

of the carcass (Ramsbottom et al., 1945; Jones et al., 2001). Rhee et al. (2004) found that

the adductor, semimembranosus, gluteus medius, and semitendinosus all from the round;

and the supraspinatus from the chuck had high Warner-Bratzler shear force values (WBS









= 4.29 kg). Savell and Smith (2000) reported that the chuck represents about 30% of the

total carcass weight. That is approximately 52% of the carcass that is currently used

primarily as ground beef and roasts.

Miller et al. (2001) found that consumers were willing to pay a premium for steaks

that reach certain levels of tenderness. One of the most prevalent and non-invasive

methods of postmortem tenderization is "aging" meat at refrigerated temperatures

(Parrish, 1997). Thaw loss and cook loss could be of concern when aging meat though

(Mitchell et al., 1991). However, that study did not report significant differences in

thawing or cooking losses among aging periods. Rhee et al. (2004) found a lower

cooking loss for the biceps femoris in the round than any chuck muscles studied when

aged to 14 days. As the industry begins to isolate individual muscles of the chuck and

round for merchandising as steak cuts that will be cooked commonly with a dry cooking

method, then more knowledge about how these muscles respond to postmortem aging is

required.

The economic incentives for the industry to improve the tenderness of beef must be

established before significant improvements in the consistency and palatability of beef

will occur (Miller et al., 1998). Kukowski et al. (2004) asked panelist to assign a

price/0.45 kg (0=would not buy, 10=$10/0.45 kg). Consumers were willing to pay

$5.68/0.45 kg for the infraspinatus, and $5.15/0.45 kg for the triceps brachii. This could

provide an incentive for retailers to use these individual muscles as steak cuts. Other cuts

from the Kukowski et al. (2004) study that were found to be acceptable as steaks cuts

were the serratus ventralis ($4.78/0.45 kg), and the complexus ($4.75/0.45 kg).









According to Miller et al. (1998), the most important factor in a tenderness study with

consumers was to establish that a range in beef tenderness from tender to tough exists.

Continued work is needed on improving meat tenderness, primarily for retail cuts

from the round and chuck. If consumers are willing to pay more for guaranteed tender

beef products (Boleman et al., 1997), additional work needs to be conducted to

investigate aging patterns of other muscles of the chuck and round so that the highest and

best use for each muscle can be determined. And if thaw loss and cook loss is a concern

with aging, the cost and benefit of aging versus loss needs to be explored. If certain

muscles do not respond to aging then it seems a waste of resources to do so, and other

methods of ensuring tenderness need to be explored. If muscles from the chuck and

round do respond differently to aging, then targeting or customizing aging time to

individual muscles and desired level of tenderness would seem appropriate.

Materials and Methods

Institutional Meat Purchase Specifications (IMPS) (North American Meat

Processors, 1988) 115 2-piece boneless chucks and IMPS 167A peeled knuckles were

purchased from a major packer of known USDA grade and slaughter date. Two grades of

cuts were studied: USDA Select and the upper 2/3 of the USDA Choice grade. Eight

subprimals of each grade were immediately shipped to the University of Florida Meats

Laboratory for muscle separation. The IMPS 115 2-piece chuck was separated and the

following muscles were selected for study: infraspinatus, triceps brachii lateral head,

triceps brachii long head, serratus ventralis, complexus, splenius, and rhomboideus.

The IMPS 167A knuckle was also separated and the vastus lateralis and rectus femoris

were evaluated. These nine muscles were selected because of the possibility that these

could be used as steak cuts where tenderness is critical due to the probability that they









would be cooked with a dry cooking method, based on results from the Muscle Profiling

Study conducted by University of Florida and University of Nebraska in conjunction with

National Cattleman's Beef Association (NCBA, 2000).

Each muscle was divided into four portions, progressing from anterior to posterior

orientation to the carcass, or from dorsal to ventral orientation to the carcass depending

on muscle fiber orientation: A was the 1st 25% portion of the muscle, B was the 2nd 25%

portion of the muscle, C was the 3rd 25% portion of the muscle, and D was the 4th 25%

portion of the muscle. One steak was removed for evaluation from each portion of the

muscle to be studied. For small muscles the entire portion may have been used as the

steak. Postmortem aging was conducted for 7, 14, 21, or 28 days at 2 + 20C cooler

temperature. Individual steaks were vacuum sealed in Cryovac B550T (Sealed Air Corp.,

Duncan, SC) bags and subsequently heat shrunk in 820C water as per manufactures

recommendation. A Latin square was used to assign each steak into one of four

postmortem aging treatments. There were eight 2 piece chucks from the USDA Select

grade numbered one through eight, and eight knuckles from the USDA Select grade

numbered one though eight. The same numbering system was used for the subprimals

from the USDA Choice grade. For pieces one through four, the postmortem aging period

was rotated clockwise for each location. For pieces five through eight, the positions for

postmortem aging period was rotated counter-clockwise. This was done to remove

muscle location effect. Also, this treatment allocation method allowed for location effect

to be tested and determined statistically.

After achieving the appropriate postmortem aging treatment, steaks were frozen at -

400 C then transferred to a -200 C holding freezer until analysis could be conducted.









Eight of each of the subprimals for each grade were sampled and replicated twice for a

total of 32 subprimals boned to generate 288 muscles. Four steaks per muscle produced

1152 observations for this trial.

Steaks were thawed for 18 hours at 2 to 40 C then broiled on Farberware

(Farberware, Bronx, NY) open-hearth broilers to an internal temperature of 71C

(American Meat Science Association, 1995). The housing and drip pans of each broiler

were covered with aluminum foil and preheated for 15 min. Copper-constantan

thermocouples attached to a potentiometer were placed in the approximate geometric

center of each steak and used to record internal temperature. Steaks were turned when

the internal temperature of 350 C was reached and removed from the broiler when the

internal temperature reached 710C. Weight in grams was taken while the steaks were

frozen, after thawing, and after cooking for calculation of cook loss and thaw loss.

Least squares, fixed model procedures of SAS (2001) were used to analyze these

data. This study was analyzed as a split-plot design where quality grade and muscle was

the main-plot and postmortem aging and location were the sub-plots which were assigned

using a Latin square design.

Results and Discussion

Thaw loss mean values and standard error means (SEM) are shown in Table 4-1 for

the nine muscles averaged across all aging periods. The infraspinatus had the lowest

amount of thaw loss, followed by the rectus femoris, splenius. The rhomboideus and the

complexus had by far the most thaw loss, with the vastus lateralis and the triceps both

lateral and long head being similar. The serratus was intermediate for thaw loss.

Compared to Warner-Bratzler (WBS) shear force for the same nine muscles, from the

previous chapter, the rhomboideus and the vastus lateralis were in the least tender tier of









muscles also. The infraspinatus had both the lowest amount of thaw loss and the lowest

WBS. The thaw loss percentage could have an effect on the endpoint tenderness. The

aging treatment did not have an effect on thaw loss.

The interaction of grade by age is shown in Figure 4-1. As USDA Select grade was

aged from 7 to 21 days, there was an increased percentage of thaw loss. However, after

14 to 21 days of age, it seems that there is not further increase in thaw loss percentages.

For USDA Choice grade, there was in increase from 14 to 28 days of aging. There is not

a difference in thaw loss for steaks from the USDA Choice grade aged from 7 to 14 days.

It seems also that by 28 days of aging, there were no significant differences in steaks

from either the USDA Choice or the USDA Select grades

The splenius and vastus lateralis and triceps brachii lateral head had the largest

amount of cook loss as shown in Table 4-2. The triceps brachii long head, the rectus

femoris and the infraspinatus followed these muscles. The muscles with the least amount

of loss were the serratus ventralis, rhomboideus and the complexus. The splenius,

complexus and rhomboideus had low thaw losses and subsequently higher cook losses as

compared to other muscles. Rhee et al. (2004) reported that the infraspinatus and the

triceps brachii had low cook losses after 14 days of age. This is consistent with the

findings of the current study with the exception of the higher cook loss for the triceps

brachii lateral head.

The analysis of variance revealed a grade by muscle interaction effect (Figure 4-2).

The muscles responded differently depending on grade. The most significant cook loss

was observed for the triceps brachii- lateral head and the serratus ventralis. The

explanation of this is not clearly obvious but could be due to the amount of exposed









muscle fibers during the cooking process. The muscle fibers from these steaks run in a

fan shaped pattern allowing for more detrimental effects of heat to the fibers. Another

possibility is the amount of connective tissue that is located within these muscles. There

could be a great cook loss with a higher amount of connective tissue although Mitchell et

al. (1991) and Jones et al. (1992) did not observe this difference. This difference may

have been seen in the infraspinatus also if the connective tissue had not been trimmed

from the muscle prior to steak separation.

All other muscles had less observable losses for both the USDA Select and USDA

Choice steaks. The triceps brachii long head and to a less extent, the rhomboideus had a

slightly higher cook loss for USDA Choice, but it was not significant. Berry and Leddy

(1990) observed a lower cooking loss for USDA Select steaks than USDA Choice steaks

when the steaks were broiled. This does not agree with the current study where USDA

Select had a higher amount of cooking loss than did USDA Choice.

The interaction effect of age by subprimal approached a level of significance with

P=0.071). This interaction is shown in Figure 4-3. As the chuck was aged from 7 to 28

days, the cook loss tended to increased. With the knuckle, the cook loss tended to

decrease from 7 to 14 days of aging and from 21 to 28 days of aging. Cook loss

remained consistent from 14 to 21 days of aging. There are more detrimental effects to

steaks from the knuckle when they are aged from 14 to 21 days. Rhee et al. (2004)

reported that low biceps femoris cook losses were unique among muscles from the round.

It seems that in the current study, there is a larger cook loss associated with muscles from

the knuckle.









The majority of researchers have not reported a significant difference in cook losses

and thaw losses among grade or muscle (Mitchell et al., 1991; Jones et al., 1992;

Shackelford et al., 1997) with the exception of higher cook losses when steaks are cooked

with a belt grill.

Implications

There is a greater amount of thaw loss and cook loss for steaks from USDA Select

than for steaks from USDA Choice grades. Further research needs to be conducted to

discover why. Aging USDA Select grade from 14 to 21 days seems to reduce the

likelihood that further increases in thaw loss percentages will occur. For USDA Choice

grade there is no differences in thaw loss until after 14 days of postmortem aging. After

28 days of aging there is no difference in thaw loss steaks between the USDA Choice or

the USDA Select grades. It is suggested that aging past 14 days will increase thaw loss,

but cook loss is possibly only affected by cooking method as suggested by Shackelford et

al. 1997).












Table 4-1. Thaw loss for muscles of the chuck and knuckle averaged across all aging periods
Subprimal Muscle Mean, % SEM
Chuck Triceps lateral head 3.8c 0.23
Triceps long head 3.8bcd 0.23
Splenius 3.2de 0.23
Complexus 4.9a 0.23
Rhomboideus 4.5" 0.23
Serratus ventralis 3.5cd 0.23
Infraspinatus 2.2f 0.23
Knuckle Vastus lateralis 4.2ac 0.23
Rectus femoris 3.1e 0.23
abcdet Means with the same superscript in the same column are not significantly different at P<0.05. Each muscle mean is an average
of 768 measurements.












Table 4-2. Cook loss for muscles of the chuck and knuckle averaged across all aging periods
Subprimal Muscle Mean, % SEM
Chuck Triceps lateral head 32.4ab 0.50
Triceps long head 31.1bcde 0.50
Splenius 33.6a 0.51
Complexus 30.8cde 0.51
Rhomboideus 30.5de 0.51
Serratus ventralis 30.0e 0.50
Infraspinatus 30.9bcd 0.50
Knuckle Vastus lateralis 32.3ab 0.50
Rectus femoris 31.6bcd 0.50
abcde Means with the same superscript in the same column are not significantly different at P<0.05. Each muscle mean is an average of
768 measurements.















-*- Select Top Choice


5
a
4.5
4.5 ab T ..- abc

4

3.5

3T


S2.5

2

1.5

1

0.5

O
7 14 21 28
Aging period, days

abcMeans with the same superscript are not significantly different at P measurements.


Figure 4-1. Thaw loss average for grades across aging periods.










U Select E Top Choice -


ab bc


Sbcdefg
71 4


bcde
JTh
-,-,A


ef efg


cdefg
-


defg
['II


f //1,/ /


abcdegfhMeans with the same superscript in the are not significantly different at P<0.05. Each
average of 384 measurements.

Figure 4-2. Cook loss for muscles by grade.


/
/


i
/


muscle mean at each grade is an


efg


defg
.-Th















-1- Chuck -- Knuckle


34


abc
33
c abc


c / Tab
Na
31 -
lab 4000,
abc
30


29


28


27
7 14 21 28
Aging period, days
abcMeans with the same superscript are not significantly different at P<0.05. Each chuck mean is an average of 1,344
measurements. Each knuckle mean is an average of 384 measurements.


Figure 4-3. Cook loss of subprimals averaged across grade by aging period.














CHAPTER 5
CONCLUSIONS

Postmortem aging affects all of the muscles evaluated in this study in a similar

fashion. Therefore, consistent recommendations about postmortem aging can be given

for these muscles of locomotion. This study revealed that USDA grade would have an

effect on postmortem aging, in that for muscles from the upper two-thirds of USDA

Choice grade were not significantly improved after seven days postmortem aging.

Muscles from the USDA Select grade should be aged a minimum of 14 days postmortem

to achieve optimum tenderness.

Location within a muscle was found to have an effect on Wamer-Bratzler shear

values in four of the nine muscles evaluated. This indicated that muscles would have to

be treated on an individual basis when fabricating and merchandising individual retail

cuts or portions from muscles of the chuck and round. For some muscles, location within

the cut can be ignored and for others location must be considered for tenderness

enhancement or product utilization.

There was a greater amount of thaw loss and cook loss for steaks from USDA

Select than for USDA Choice grades. It was not entirely obvious as to why, so further

research needs to be conducted. Aging USDA Select grades from 14 to 21 days seems to

reduce the likelihood that further increases in thaw loss percentages will occur. For

USDA Choice grades, there was no difference in thaw loss until 14 days. After 28 days

of aging there was no difference in thaw loss of steaks between the USDA Choice and the






56


USDA Select grades. Aging past 14 days postmortem will increase thaw loss, but cook

loss is possibly only affected by cooking method.
















LIST OF REFERENCES


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significance of factors influencing and/or associated with beef tenderness. Proc.
11th Research Conf., Am. Meat Inst. Found. Circ., p. 85.

Alsmeyer, R. L., J. W. Thornton, and R. L. Hiner. 1965. Some dorsal-lateral location
tenderness differences in the longissimus dorsi muscle of beef and pork. J. Anim.
Sci. 24:526.

Alsmeyer, R. L., J. W. Thornton, R. L. Hiner and N. C. Bollinger. 1966. Beef and pork
tenderness measured by the press, Warner-Bratzler and STE methods. Food
Technol. 20:115.

American Meat Science Association. 1995. Research guidelines for cookery, sensory
evaluation, and instrumental tenderness measurements of fresh meat. Am. Meat
Sci. Assoc. and Nat. Live Stock and Meat Board.

Berry, B. W., and K. F. Leddy. 1990. Comparison of restaurant vs. research-type broiling
with beef loin steaks differing in marbling. J. Anim. Sci. 68:666.

Boleman, S. J., S. L. Boleman, R. K. Miller, J. F. Taylor, H. R. Cross, T. L. Wheeler, M.
Koohmararie, S. D. Shackelford, M. F. Miller, R. L. West, D. D. Johnson, J. W.
Savell. 1997. Consumer evaluation of beef of known categories of tenderness. J.
Anim. Sci. 75:1521.

Blumer, T. N. 1963. Relationship of marbling to the palatability of beef. J. Anim. Sci.
22:771.

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BIOGRAPHICAL SKETCH

Christy Lynn Greenhaw Bratcher was born in Huntsville, Alabama on October 23,

1979. She spent the first 11 years of life in a small town in North Alabama called Arab.

In 1991, she moved to Daytona Beach, Florida, with her parents and brother. After high

school, Christy attended the University of Florida pursuing a degree in animal sciences to

ultimately become a large animal veterinarian. During the first two years of college, she

became interested in meat sciences and specialized her animal sciences degree by

pursuing the option of food safety and meats processing. During her undergraduate

program, Christy was involved with Gator Collegiate Cattlewomen and Alpha Zeta, as

well as holding a job as a veterinarian technician and then an assistant at the University of

Florida Meat Processing Center, and did an internship with Buckhead Beef in Atlanta,

Georgia, for 3 months. This internship became a part-time position for her as she

finished her Bachelor of Science degree. She also became the teaching assistant for ANS

2002, The Meat We Eat, from Fall 2001 to Spring 2002. These experiences guided

Christy to pursue a Master of Science degree in animal sciences, after graduating with a

Bachelor of Science degree in Spring of 2002.

Also, while pursuing her undergraduate degree, Christy was married to Michael

Bratcher in May of 1999. Michael was pursuing a degree at the University of Florida in

exercise and sport sciences with the goal of becoming a physical education teacher and

football coach.






67


In August 2002, Christy was accepted to a graduate research and teaching program

at the University of Florida Department of Animal Sciences under the direction of Dr. W.

Dwain Johnson. Her major responsibility during the program was to teach ANS 2002,

The Meat We Eat, and to assist with other meat science undergraduate courses. In the

2003-2004 school year Christy was the recipient of the Jack Fry Graduate Teaching

Award for the College of Agricultural and Life Sciences. As a graduate student she was

involved with the Animal Sciences Graduate Student Association and the Graduate

Student Council.